[PATCH 0/3] tools/accounting: refactor delay fields and share format_timespec()

[PATCH 0/3] tools/accounting: refactor delay fields and share format_timespec()

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

- Convert per-field delay members in struct task_info to an array indexed
  by enum delay_type, eliminating offsetof() pointer arithmetic.

- Factor out a common format_timespec() implementation shared by getdelays
  and delaytop, using strftime for cleaner timestamp formatting.

- Replace the complex sizeof/ULL/shift Y2038 guard with a direct narrowing
  truncation check ((long long)time_sec != ts->tv_sec).

Wang Yaxin (3):
  delaytop: refactor repetitive delay fields into array with enum
  tools/accounting: factor out shared format_timespec() implementation
  tools/accounting: simplify 32-bit time_t overflow check in
    format_timespec()

 tools/accounting/Makefile             |  12 +-
 tools/accounting/delaytop.c           | 261 +++++++++-----------------
 tools/accounting/format_timespec.c    |  37 ++++
 tools/accounting/format_timespec.h    |   9 +
 tools/accounting/getdelays.c          |  32 +---
 tools/include/uapi/linux/time_types.h |  18 ++
 6 files changed, 169 insertions(+), 200 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

-- 
2.27.0

[PATCH 1/3] delaytop: refactor repetitive delay fields into array with enum

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

Replace the 9 groups of (count, delay_total, delay_max, delay_max_ts)
named fields in struct task_info with a struct delay_metrics array
indexed by enum delay_type. This eliminates all unsafe pointer
arithmetic via offsetof() from compare_tasks(),
field_delay_max_and_ts(), and get_field_delay_values().

The struct field_desc now stores an enum delay_type index instead of
four separate unsigned long offset values.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
---
 tools/accounting/delaytop.c | 220 +++++++++++++++---------------------
 1 file changed, 88 insertions(+), 132 deletions(-)

diff --git a/tools/accounting/delaytop.c b/tools/accounting/delaytop.c
index 1c40bb477320..f1d26ff98792 100644
--- a/tools/accounting/delaytop.c
+++ b/tools/accounting/delaytop.c
@@ -61,31 +61,51 @@
 #define MAX_MSG_SIZE	1024
 #define MAX_TASKS		1000
 #define MAX_BUF_LEN		256
-#define SET_TASK_STAT(task_count, field) tasks[task_count].field = stats.field
 #define BOOL_FPRINT(stream, fmt, ...) \
 ({ \
 	int ret = fprintf(stream, fmt, ##__VA_ARGS__); \
 	ret >= 0; \
 })
-#define TASK_AVG(task, field) average_ms((task).field##_delay_total, (task).field##_count)
+#define TASK_AVG(task, type) \
+	average_ms((task).delays[DELAY_##type].delay_total, \
+		   (task).delays[DELAY_##type].count)
 #define PSI_LINE_FORMAT "%-12s %6.1f%%/%6.1f%%/%6.1f%%/%8llu(ms)\n"
 #define DELAY_FMT_DEFAULT "%8.2f %8.2f %8.2f %8.2f\n"
 #define DELAY_FMT_MEMVERBOSE "%8.2f %8.2f %8.2f %8.2f %8.2f %8.2f\n"
-#define SORT_FIELD(name, cmd, modes) \
-	{#name, #cmd, \
-	offsetof(struct task_info, name##_delay_total), \
-	offsetof(struct task_info, name##_count), \
-	offsetof(struct task_info, name##_delay_max), \
-	offsetof(struct task_info, name##_delay_max_ts), \
-	modes}
-#define SORT_FIELD_NO_MAX(name, cmd, modes) \
-	{#name, #cmd, \
-	offsetof(struct task_info, name##_delay_total), \
-	offsetof(struct task_info, name##_count), \
-	0, \
-	0, \
-	modes}
-#define END_FIELD {NULL, 0, 0, 0, 0, 0, 0}
+#define COPY_DELAY(task_idx, type, stats_prefix) \
+	do { \
+		tasks[task_idx].delays[DELAY_##type].count = \
+			stats.stats_prefix##_count; \
+		tasks[task_idx].delays[DELAY_##type].delay_total = \
+			stats.stats_prefix##_delay_total; \
+		tasks[task_idx].delays[DELAY_##type].delay_max = \
+			stats.stats_prefix##_delay_max; \
+		tasks[task_idx].delays[DELAY_##type].delay_max_ts = \
+			stats.stats_prefix##_delay_max_ts; \
+	} while (0)
+#define SORT_FIELD(name, cmd, type, modes, has_max) \
+	{#name, #cmd, type, modes, has_max}
+#define END_FIELD {NULL, 0, 0, 0, false}
+
+enum delay_type {
+	DELAY_CPU,
+	DELAY_BLKIO,
+	DELAY_SWAPIN,
+	DELAY_FREEPAGES,
+	DELAY_THRASHING,
+	DELAY_COMPACT,
+	DELAY_WPCOPY,
+	DELAY_IRQ,
+	DELAY_MEM,
+	NUM_DELAY_TYPES
+};
+
+struct delay_metrics {
+	unsigned long long count;
+	unsigned long long delay_total;
+	unsigned long long delay_max;
+	struct __kernel_timespec delay_max_ts;
+};

 /* Display mode types */
 #define MODE_TYPE_ALL	(0xFFFFFFFF)
@@ -116,40 +136,7 @@ struct task_info {
 	int pid;
 	int tgid;
 	char command[TASK_COMM_LEN];
-	unsigned long long cpu_count;
-	unsigned long long cpu_delay_total;
-	unsigned long long cpu_delay_max;
-	struct __kernel_timespec cpu_delay_max_ts;
-	unsigned long long blkio_count;
-	unsigned long long blkio_delay_total;
-	unsigned long long blkio_delay_max;
-	struct __kernel_timespec blkio_delay_max_ts;
-	unsigned long long swapin_count;
-	unsigned long long swapin_delay_total;
-	unsigned long long swapin_delay_max;
-	struct __kernel_timespec swapin_delay_max_ts;
-	unsigned long long freepages_count;
-	unsigned long long freepages_delay_total;
-	unsigned long long freepages_delay_max;
-	struct __kernel_timespec freepages_delay_max_ts;
-	unsigned long long thrashing_count;
-	unsigned long long thrashing_delay_total;
-	unsigned long long thrashing_delay_max;
-	struct __kernel_timespec thrashing_delay_max_ts;
-	unsigned long long compact_count;
-	unsigned long long compact_delay_total;
-	unsigned long long compact_delay_max;
-	struct __kernel_timespec compact_delay_max_ts;
-	unsigned long long wpcopy_count;
-	unsigned long long wpcopy_delay_total;
-	unsigned long long wpcopy_delay_max;
-	struct __kernel_timespec wpcopy_delay_max_ts;
-	unsigned long long irq_count;
-	unsigned long long irq_delay_total;
-	unsigned long long irq_delay_max;
-	struct __kernel_timespec irq_delay_max_ts;
-	unsigned long long mem_count;
-	unsigned long long mem_delay_total;
+	struct delay_metrics delays[NUM_DELAY_TYPES];
 };

 /* Container statistics structure */
@@ -165,11 +152,9 @@ struct container_stats {
 struct field_desc {
 	const char *name;	/* Field name for cmdline argument */
 	const char *cmd_char;	/* Interactive command */
-	unsigned long total_offset; /* Offset of total delay in task_info */
-	unsigned long count_offset; /* Offset of count in task_info */
-	unsigned long max_offset;  /* Offset of max delay in task_info */
-	unsigned long max_ts_offset; /* Offset of max delay timestamp in task_info */
+	enum delay_type type;	/* Index into task_info.delays[] */
 	size_t supported_modes; /* Supported display modes */
+	bool has_max;		/* Whether this field has max/ts */
 };

 /* Program settings structure */
@@ -193,15 +178,15 @@ static int task_count;
 static int running = 1;
 static struct container_stats container_stats;
 static const struct field_desc sort_fields[] = {
-	SORT_FIELD(cpu,		c,	MODE_DEFAULT | MODE_TYPE),
-	SORT_FIELD(blkio,	i,	MODE_DEFAULT | MODE_TYPE),
-	SORT_FIELD(irq,		q,	MODE_DEFAULT | MODE_TYPE),
-	SORT_FIELD_NO_MAX(mem,	m,	MODE_DEFAULT | MODE_MEMVERBOSE),
-	SORT_FIELD(swapin,	s,	MODE_MEMVERBOSE | MODE_TYPE),
-	SORT_FIELD(freepages,	r,	MODE_MEMVERBOSE | MODE_TYPE),
-	SORT_FIELD(thrashing,	t,	MODE_MEMVERBOSE | MODE_TYPE),
-	SORT_FIELD(compact,	p,	MODE_MEMVERBOSE | MODE_TYPE),
-	SORT_FIELD(wpcopy,	w,	MODE_MEMVERBOSE | MODE_TYPE),
+	SORT_FIELD(cpu, c, DELAY_CPU, MODE_DEFAULT | MODE_TYPE, true),
+	SORT_FIELD(blkio, i, DELAY_BLKIO, MODE_DEFAULT | MODE_TYPE, true),
+	SORT_FIELD(irq, q, DELAY_IRQ, MODE_DEFAULT | MODE_TYPE, true),
+	SORT_FIELD(mem, m, DELAY_MEM, MODE_DEFAULT | MODE_MEMVERBOSE, false),
+	SORT_FIELD(swapin, s, DELAY_SWAPIN, MODE_MEMVERBOSE | MODE_TYPE, true),
+	SORT_FIELD(freepages, r, DELAY_FREEPAGES, MODE_MEMVERBOSE | MODE_TYPE, true),
+	SORT_FIELD(thrashing, t, DELAY_THRASHING, MODE_MEMVERBOSE | MODE_TYPE, true),
+	SORT_FIELD(compact, p, DELAY_COMPACT, MODE_MEMVERBOSE | MODE_TYPE, true),
+	SORT_FIELD(wpcopy, w, DELAY_WPCOPY, MODE_MEMVERBOSE | MODE_TYPE, true),
 	END_FIELD
 };
 static int sort_selected;
@@ -433,20 +418,20 @@ static void parse_args(int argc, char **argv)
 /* Calculate average delay in milliseconds for overall memory */
 static void set_mem_delay_total(struct task_info *t)
 {
-	t->mem_delay_total = t->swapin_delay_total +
-		t->freepages_delay_total +
-		t->thrashing_delay_total +
-		t->compact_delay_total +
-		t->wpcopy_delay_total;
+	t->delays[DELAY_MEM].delay_total = t->delays[DELAY_SWAPIN].delay_total +
+		t->delays[DELAY_FREEPAGES].delay_total +
+		t->delays[DELAY_THRASHING].delay_total +
+		t->delays[DELAY_COMPACT].delay_total +
+		t->delays[DELAY_WPCOPY].delay_total;
 }

 static void set_mem_count(struct task_info *t)
 {
-	t->mem_count = t->swapin_count +
-		t->freepages_count +
-		t->thrashing_count +
-		t->compact_count +
-		t->wpcopy_count;
+	t->delays[DELAY_MEM].count = t->delays[DELAY_SWAPIN].count +
+		t->delays[DELAY_FREEPAGES].count +
+		t->delays[DELAY_THRASHING].count +
+		t->delays[DELAY_COMPACT].count +
+		t->delays[DELAY_WPCOPY].count;
 }

 /* Create a raw netlink socket and bind */
@@ -758,38 +743,14 @@ static void fetch_and_fill_task_info(int pid, const char *comm)
 						strncpy(tasks[task_count].command, comm,
 							TASK_COMM_LEN - 1);
 						tasks[task_count].command[TASK_COMM_LEN - 1] = '\0';
-						SET_TASK_STAT(task_count, cpu_count);
-						SET_TASK_STAT(task_count, cpu_delay_total);
-						SET_TASK_STAT(task_count, cpu_delay_max);
-						SET_TASK_STAT(task_count, cpu_delay_max_ts);
-						SET_TASK_STAT(task_count, blkio_count);
-						SET_TASK_STAT(task_count, blkio_delay_total);
-						SET_TASK_STAT(task_count, blkio_delay_max);
-						SET_TASK_STAT(task_count, blkio_delay_max_ts);
-						SET_TASK_STAT(task_count, swapin_count);
-						SET_TASK_STAT(task_count, swapin_delay_total);
-						SET_TASK_STAT(task_count, swapin_delay_max);
-						SET_TASK_STAT(task_count, swapin_delay_max_ts);
-						SET_TASK_STAT(task_count, freepages_count);
-						SET_TASK_STAT(task_count, freepages_delay_total);
-						SET_TASK_STAT(task_count, freepages_delay_max);
-						SET_TASK_STAT(task_count, freepages_delay_max_ts);
-						SET_TASK_STAT(task_count, thrashing_count);
-						SET_TASK_STAT(task_count, thrashing_delay_total);
-						SET_TASK_STAT(task_count, thrashing_delay_max);
-						SET_TASK_STAT(task_count, thrashing_delay_max_ts);
-						SET_TASK_STAT(task_count, compact_count);
-						SET_TASK_STAT(task_count, compact_delay_total);
-						SET_TASK_STAT(task_count, compact_delay_max);
-						SET_TASK_STAT(task_count, compact_delay_max_ts);
-						SET_TASK_STAT(task_count, wpcopy_count);
-						SET_TASK_STAT(task_count, wpcopy_delay_total);
-						SET_TASK_STAT(task_count, wpcopy_delay_max);
-						SET_TASK_STAT(task_count, wpcopy_delay_max_ts);
-						SET_TASK_STAT(task_count, irq_count);
-						SET_TASK_STAT(task_count, irq_delay_total);
-						SET_TASK_STAT(task_count, irq_delay_max);
-						SET_TASK_STAT(task_count, irq_delay_max_ts);
+						COPY_DELAY(task_count, CPU, cpu);
+						COPY_DELAY(task_count, BLKIO, blkio);
+						COPY_DELAY(task_count, SWAPIN, swapin);
+						COPY_DELAY(task_count, FREEPAGES, freepages);
+						COPY_DELAY(task_count, THRASHING, thrashing);
+						COPY_DELAY(task_count, COMPACT, compact);
+						COPY_DELAY(task_count, WPCOPY, wpcopy);
+						COPY_DELAY(task_count, IRQ, irq);
 						set_mem_count(&tasks[task_count]);
 						set_mem_delay_total(&tasks[task_count]);
 						task_count++;
@@ -912,10 +873,10 @@ static int compare_tasks(const void *a, const void *b)
 		return 0;
 	}

-	total1 = *(unsigned long long *)((char *)t1 + cfg.sort_field->total_offset);
-	total2 = *(unsigned long long *)((char *)t2 + cfg.sort_field->total_offset);
-	count1 = *(unsigned long long *)((char *)t1 + cfg.sort_field->count_offset);
-	count2 = *(unsigned long long *)((char *)t2 + cfg.sort_field->count_offset);
+	total1 = t1->delays[cfg.sort_field->type].delay_total;
+	total2 = t2->delays[cfg.sort_field->type].delay_total;
+	count1 = t1->delays[cfg.sort_field->type].count;
+	count2 = t2->delays[cfg.sort_field->type].count;

 	avg1 = average_ms(total1, count1);
 	avg2 = average_ms(total2, count2);
@@ -929,22 +890,17 @@ static int compare_tasks(const void *a, const void *b)
 static void field_delay_max_and_ts(const struct task_info *task, const struct field_desc *field,
 				     unsigned long long *max_ns, struct __kernel_timespec *max_ts)
 {
-	if (!field || !field->max_offset) {
+	if (!field || !field->has_max) {
 		*max_ns = 0;
 		if (max_ts)
 			memset(max_ts, 0, sizeof(*max_ts));
 		return;
 	}

-	*max_ns = *(unsigned long long *)((char *)task + field->max_offset);
+	*max_ns = task->delays[field->type].delay_max;

-	if (max_ts) {
-		if (field->max_ts_offset)
-			*max_ts = *(struct __kernel_timespec *)((char *)task +
-							       field->max_ts_offset);
-		else
-			memset(max_ts, 0, sizeof(*max_ts));
-	}
+	if (max_ts)
+		*max_ts = task->delays[field->type].delay_max_ts;
 }

 /* Get delay values for a specific field */
@@ -954,15 +910,15 @@ static void get_field_delay_values(const struct task_info *task, const struct fi
 {
 	unsigned long long total, count, max;

-	if (!field || !field->max_offset) {
+	if (!field) {
 		*avg_ms = 0;
 		*max_ms = 0;
 		memset(max_ts, 0, sizeof(*max_ts));
 		return;
 	}

-	total = *(unsigned long long *)((char *)task + field->total_offset);
-	count = *(unsigned long long *)((char *)task + field->count_offset);
+	total = task->delays[field->type].delay_total;
+	count = task->delays[field->type].count;
 	*avg_ms = average_ms(total, count);

 	field_delay_max_and_ts(task, field, &max, max_ts);
@@ -1180,18 +1136,18 @@ static void display_results(int psi_ret)
 				avg_ms, max_ms, format_kernel_timespec(&max_ts));
 		} else if (cfg.display_mode == MODE_MEMVERBOSE) {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_MEMVERBOSE,
-				TASK_AVG(tasks[i], mem),
-				TASK_AVG(tasks[i], swapin),
-				TASK_AVG(tasks[i], freepages),
-				TASK_AVG(tasks[i], thrashing),
-				TASK_AVG(tasks[i], compact),
-				TASK_AVG(tasks[i], wpcopy));
+				TASK_AVG(tasks[i], MEM),
+				TASK_AVG(tasks[i], SWAPIN),
+				TASK_AVG(tasks[i], FREEPAGES),
+				TASK_AVG(tasks[i], THRASHING),
+				TASK_AVG(tasks[i], COMPACT),
+				TASK_AVG(tasks[i], WPCOPY));
 		} else {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_DEFAULT,
-				TASK_AVG(tasks[i], cpu),
-				TASK_AVG(tasks[i], blkio),
-				TASK_AVG(tasks[i], irq),
-				TASK_AVG(tasks[i], mem));
+				TASK_AVG(tasks[i], CPU),
+				TASK_AVG(tasks[i], BLKIO),
+				TASK_AVG(tasks[i], IRQ),
+				TASK_AVG(tasks[i], MEM));
 		}
 	}

-- 
2.27.0

Re: [PATCH 1/3] delaytop: refactor repetitive delay fields into array with enum

[xu.xin16]

> Replace the 9 groups of (count, delay_total, delay_max, delay_max_ts)
> named fields in struct task_info with a struct delay_metrics array
> indexed by enum delay_type. This eliminates all unsafe pointer
> arithmetic via offsetof() from compare_tasks(),
> field_delay_max_and_ts(), and get_field_delay_values().
> 
> The struct field_desc now stores an enum delay_type index instead of
> four separate unsigned long offset values.
> 
> Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>

Acked-by: Xu Xin <xu.xin16@zte.com.cn>

[PATCH 2/3] tools/accounting: factor out shared format_timespec() implementation

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

The same __kernel_timespec formatting logic existed independently in
both getdelays.c and delaytop.c with minor differences (strftime vs
snprintf, __kernel_time64_t vs time_t).

Create a shared format_timespec.c/h with a canonical implementation
(strftime + time_t), remove the static copies from both files, and
link both programs against the common object.

Also simplify the Makefile with a pattern rule for %.o and a static
pattern rule for the two programs that need format_timespec.o.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
---
 tools/accounting/Makefile             | 12 ++++++++-
 tools/accounting/delaytop.c           | 39 +++------------------------
 tools/accounting/format_timespec.c    | 39 +++++++++++++++++++++++++++
 tools/accounting/format_timespec.h    |  9 +++++++
 tools/accounting/getdelays.c          | 32 ++--------------------
 tools/include/uapi/linux/time_types.h | 18 +++++++++++++
 6 files changed, 82 insertions(+), 67 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

diff --git a/tools/accounting/Makefile b/tools/accounting/Makefile
index 007c0bb8cbbb..22e690c853a5 100644
--- a/tools/accounting/Makefile
+++ b/tools/accounting/Makefile
@@ -3,8 +3,18 @@ CC := $(CROSS_COMPILE)gcc
 CFLAGS := -I../include/uapi/

 PROGS := getdelays procacct delaytop
+OBJS := format_timespec.o

 all: $(PROGS)

+getdelays delaytop: %: %.o $(OBJS)
+	$(CC) $(CFLAGS) -o $@ $^
+
+procacct: procacct.o
+	$(CC) $(CFLAGS) -o $@ $^
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
 clean:
-	rm -fr $(PROGS)
+	rm -fr $(PROGS) *.o
diff --git a/tools/accounting/delaytop.c b/tools/accounting/delaytop.c
index f1d26ff98792..1144ca325447 100644
--- a/tools/accounting/delaytop.c
+++ b/tools/accounting/delaytop.c
@@ -44,6 +44,8 @@
 #include <linux/cgroupstats.h>
 #include <stddef.h>

+#include "format_timespec.h"
+
 #define PSI_PATH	"/proc/pressure"
 #define PSI_CPU_PATH	"/proc/pressure/cpu"
 #define PSI_MEMORY_PATH	"/proc/pressure/memory"
@@ -817,41 +819,6 @@ static double average_ms(unsigned long long total, unsigned long long count)
 	return (double)total / 1000000.0 / count;
 }

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DDTHH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_kernel_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	time_t time_sec;
-	struct tm tm_info;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation: check if timestamp fits in time_t on 32-bit platforms */
-	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = (time_t)ts->tv_sec;
-
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d",
-		tm_info.tm_year + 1900,
-		tm_info.tm_mon + 1,
-		tm_info.tm_mday,
-		tm_info.tm_hour,
-		tm_info.tm_min,
-		tm_info.tm_sec);
-
-	return buffer;
-}
-
 /* Comparison function for sorting tasks */
 static int compare_tasks(const void *a, const void *b)
 {
@@ -1133,7 +1100,7 @@ static void display_results(int psi_ret)
 					&max_ms, &max_ts);

 			suc &= BOOL_FPRINT(out, "%12.2f %12.2f %20s\n",
-				avg_ms, max_ms, format_kernel_timespec(&max_ts));
+				avg_ms, max_ms, format_timespec(&max_ts));
 		} else if (cfg.display_mode == MODE_MEMVERBOSE) {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_MEMVERBOSE,
 				TASK_AVG(tasks[i], MEM),
diff --git a/tools/accounting/format_timespec.c b/tools/accounting/format_timespec.c
new file mode 100644
index 000000000000..1dba50cac895
--- /dev/null
+++ b/tools/accounting/format_timespec.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shared __kernel_timespec formatting for tools/accounting/
+ *
+ * Formats a __kernel_timespec to an ISO 8601 timestamp string
+ * (YYYY-MM-DDTHH:MM:SS). Returns "N/A" if the timestamp is zero
+ * or does not fit in time_t.
+ */
+#include <time.h>
+#include <linux/time_types.h>
+#include "format_timespec.h"
+
+const char *format_timespec(const struct __kernel_timespec *ts)
+{
+	static char buffer[32];
+	struct tm tm_info;
+	time_t time_sec;
+
+	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
+		return "N/A";
+
+	/*
+	 * On 32-bit platforms time_t is 32-bit and cannot represent
+	 * dates beyond Y2038.  The kernel timestamp is always 64-bit,
+	 * so reject values that would overflow.
+	 */
+	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
+	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
+		return "N/A";
+
+	time_sec = ts->tv_sec;
+
+	if (!localtime_r(&time_sec, &tm_info))
+		return "N/A";
+
+	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
+
+	return buffer;
+}
diff --git a/tools/accounting/format_timespec.h b/tools/accounting/format_timespec.h
new file mode 100644
index 000000000000..960496ebf5c2
--- /dev/null
+++ b/tools/accounting/format_timespec.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef FORMAT_TIMESPEC_H
+#define FORMAT_TIMESPEC_H
+
+#include <linux/time_types.h>
+
+const char *format_timespec(const struct __kernel_timespec *ts);
+
+#endif
diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 6ac30d4f96f7..d3193f670d89 100644
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -30,6 +30,8 @@
 #include <linux/taskstats.h>
 #include <linux/cgroupstats.h>

+#include "format_timespec.h"
+
 /*
  * Generic macros for dealing with netlink sockets. Might be duplicated
  * elsewhere. It is recommended that commercial grade applications use
@@ -221,36 +223,6 @@ static int get_family_id(int sd)
 #define average_ms(t, c) (t / 1000000ULL / (c ? c : 1))
 #define delay_ms(t) (t / 1000000ULL)

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DD HH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	struct tm tm_info;
-	__kernel_time_t time_sec;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation on 32-bit platforms */
-	if (sizeof(time_sec) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_sec) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = ts->tv_sec;
-
-	/* Use thread-safe localtime_r */
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
-
-	return buffer;
-}
-
 /*
  * Version compatibility note:
  * Field availability depends on taskstats version (t->version),
diff --git a/tools/include/uapi/linux/time_types.h b/tools/include/uapi/linux/time_types.h
new file mode 100644
index 000000000000..375cfbdd8387
--- /dev/null
+++ b/tools/include/uapi/linux/time_types.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _TOOLS_UAPI_LINUX_TIME_TYPES_H
+#define _TOOLS_UAPI_LINUX_TIME_TYPES_H
+
+#include <linux/types.h>
+
+/*
+ * Minimal definition for use by tools/.
+ * __kernel_time64_t is always 'long long' on all architectures,
+ * so we avoid pulling in kernel-private type definitions.
+ */
+
+struct __kernel_timespec {
+	long long	tv_sec;
+	long long	tv_nsec;
+};
+
+#endif /* _TOOLS_UAPI_LINUX_TIME_TYPES_H */
-- 
2.27.0

[PATCH 3/3] tools/accounting: simplify 32-bit time_t overflow check in format_timespec()

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

Replace the Y2038 overflow guard in format_timespec() with a direct
narrowing truncation check ((long long)time_sec != ts->tv_sec), which
is both simpler and more robust across platforms. Also move the
time_sec assignment earlier to avoid duplication.

While at it, fix a minor alignment issue in delaytop.c by adding a
leading space to the output format string.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
---
 tools/accounting/delaytop.c        |  2 +-
 tools/accounting/format_timespec.c | 12 +++++-------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/tools/accounting/delaytop.c b/tools/accounting/delaytop.c
index 1144ca325447..097b57887147 100644
--- a/tools/accounting/delaytop.c
+++ b/tools/accounting/delaytop.c
@@ -1099,7 +1099,7 @@ static void display_results(int psi_ret)
 			get_field_delay_values(&tasks[i], cfg.type_field, &avg_ms,
 					&max_ms, &max_ts);

-			suc &= BOOL_FPRINT(out, "%12.2f %12.2f %20s\n",
+			suc &= BOOL_FPRINT(out, " %12.2f %12.2f %20s\n",
 				avg_ms, max_ms, format_timespec(&max_ts));
 		} else if (cfg.display_mode == MODE_MEMVERBOSE) {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_MEMVERBOSE,
diff --git a/tools/accounting/format_timespec.c b/tools/accounting/format_timespec.c
index 1dba50cac895..d7bfd307c00b 100644
--- a/tools/accounting/format_timespec.c
+++ b/tools/accounting/format_timespec.c
@@ -14,22 +14,20 @@ const char *format_timespec(const struct __kernel_timespec *ts)
 {
 	static char buffer[32];
 	struct tm tm_info;
-	time_t time_sec;
+	time_t time_sec = ts->tv_sec;

 	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
 		return "N/A";

 	/*
 	 * On 32-bit platforms time_t is 32-bit and cannot represent
-	 * dates beyond Y2038.  The kernel timestamp is always 64-bit,
-	 * so reject values that would overflow.
+	 * timestamps outside [INT32_MIN, INT32_MAX].  A 64-bit kernel
+	 * timestamp that does not survive the narrowing truncation is
+	 * rejected to avoid silent data corruption.
 	 */
-	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
+	if ((long long)time_sec != ts->tv_sec)
 		return "N/A";

-	time_sec = ts->tv_sec;
-
 	if (!localtime_r(&time_sec, &tm_info))
 		return "N/A";

-- 
2.27.0

Re: [PATCH 0/3] tools/accounting: refactor delay fields and share format_timespec()

[Andrew Morton]

On Sat, 11 Jul 2026 17:31:12 +0800 (CST) <wang.yaxin@zte.com.cn> wrote:

> - Convert per-field delay members in struct task_info to an array indexed
>   by enum delay_type, eliminating offsetof() pointer arithmetic.
> 
> - Factor out a common format_timespec() implementation shared by getdelays
>   and delaytop, using strftime for cleaner timestamp formatting.
> 
> - Replace the complex sizeof/ULL/shift Y2038 guard with a direct narrowing
>   truncation check ((long long)time_sec != ts->tv_sec).

Sounds great.

AI review might have found a couple of things.  Please check it out?
	https://sashiko.dev/#/patchset/20260711173112482SCQEM08VED2PT1pxUYOXk@zte.com.cn

[PATCH v2 0/3] tools/accounting: refactor delay fields and share format_timespec()

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

- Convert per-field delay members in struct task_info to an array indexed
  by enum delay_type, eliminating offsetof() pointer arithmetic.

- Factor out a common format_timespec() implementation shared by getdelays
  and delaytop, using strftime for cleaner timestamp formatting.

- Replace the complex sizeof/ULL/shift Y2038 guard with a direct narrowing
  truncation check ((long long)time_sec != ts->tv_sec).

Change Log
==========
v1->v2:
Only update patch 2/3 according to the suggestion:
https://sashiko.dev/#/patchset/20260711173112482SCQEM08VED2PT1pxUYOXk@zte.com.cn

1. tools/include/uapi/linux/time_types.h: expand stub to full set of
  6 structs from kernel UAPI to avoid shadowing system header
2. tools/accounting/Makefile: add $(LDFLAGS), $(LDLIBS), $(CPPFLAGS)
  to restore compatibility with standard build variables

Wang Yaxin (3):
  delaytop: refactor repetitive delay fields into array with enum
  tools/accounting: factor out shared format_timespec() implementation
  tools/accounting: simplify 32-bit time_t overflow check in
    format_timespec()

 tools/accounting/Makefile             |  12 +-
 tools/accounting/delaytop.c           | 261 +++++++++-----------------
 tools/accounting/format_timespec.c    |  37 ++++
 tools/accounting/format_timespec.h    |   9 +
 tools/accounting/getdelays.c          |  32 +---
 tools/include/uapi/linux/time_types.h |  46 +++++
 6 files changed, 197 insertions(+), 200 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

-- 
2.27.0

[PATCH 2/3] tools/accounting: factor out shared format_timespec() implementation

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

The same __kernel_timespec formatting logic existed independently in
both getdelays.c and delaytop.c with minor differences (strftime vs
snprintf, __kernel_time64_t vs time_t).

Create a shared format_timespec.c/h with a canonical implementation
(strftime + time_t), remove the static copies from both files, and
link both programs against the common object.

Also simplify the Makefile with a pattern rule for %.o and a static
pattern rule for the two programs that need format_timespec.o.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
---
 tools/accounting/Makefile             | 12 ++++++-
 tools/accounting/delaytop.c           | 39 ++---------------------
 tools/accounting/format_timespec.c    | 39 +++++++++++++++++++++++
 tools/accounting/format_timespec.h    |  9 ++++++
 tools/accounting/getdelays.c          | 32 ++-----------------
 tools/include/uapi/linux/time_types.h | 46 +++++++++++++++++++++++++++
 6 files changed, 110 insertions(+), 67 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

diff --git a/tools/accounting/Makefile b/tools/accounting/Makefile
index 007c0bb8cbbb..5224e03f5e94 100644
--- a/tools/accounting/Makefile
+++ b/tools/accounting/Makefile
@@ -3,8 +3,18 @@ CC := $(CROSS_COMPILE)gcc
 CFLAGS := -I../include/uapi/

 PROGS := getdelays procacct delaytop
+OBJS := format_timespec.o

 all: $(PROGS)

+getdelays delaytop: %: %.o $(OBJS)
+	$(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+procacct: procacct.o
+	$(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+%.o: %.c
+	$(CC) $(CPPFLAGS) $(CFLAGS) -c -o $@ $<
+
 clean:
-	rm -fr $(PROGS)
+	rm -fr $(PROGS) *.o
diff --git a/tools/accounting/delaytop.c b/tools/accounting/delaytop.c
index f1d26ff98792..1144ca325447 100644
--- a/tools/accounting/delaytop.c
+++ b/tools/accounting/delaytop.c
@@ -44,6 +44,8 @@
 #include <linux/cgroupstats.h>
 #include <stddef.h>

+#include "format_timespec.h"
+
 #define PSI_PATH	"/proc/pressure"
 #define PSI_CPU_PATH	"/proc/pressure/cpu"
 #define PSI_MEMORY_PATH	"/proc/pressure/memory"
@@ -817,41 +819,6 @@ static double average_ms(unsigned long long total, unsigned long long count)
 	return (double)total / 1000000.0 / count;
 }

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DDTHH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_kernel_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	time_t time_sec;
-	struct tm tm_info;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation: check if timestamp fits in time_t on 32-bit platforms */
-	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = (time_t)ts->tv_sec;
-
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d",
-		tm_info.tm_year + 1900,
-		tm_info.tm_mon + 1,
-		tm_info.tm_mday,
-		tm_info.tm_hour,
-		tm_info.tm_min,
-		tm_info.tm_sec);
-
-	return buffer;
-}
-
 /* Comparison function for sorting tasks */
 static int compare_tasks(const void *a, const void *b)
 {
@@ -1133,7 +1100,7 @@ static void display_results(int psi_ret)
 					&max_ms, &max_ts);

 			suc &= BOOL_FPRINT(out, "%12.2f %12.2f %20s\n",
-				avg_ms, max_ms, format_kernel_timespec(&max_ts));
+				avg_ms, max_ms, format_timespec(&max_ts));
 		} else if (cfg.display_mode == MODE_MEMVERBOSE) {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_MEMVERBOSE,
 				TASK_AVG(tasks[i], MEM),
diff --git a/tools/accounting/format_timespec.c b/tools/accounting/format_timespec.c
new file mode 100644
index 000000000000..1dba50cac895
--- /dev/null
+++ b/tools/accounting/format_timespec.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shared __kernel_timespec formatting for tools/accounting/
+ *
+ * Formats a __kernel_timespec to an ISO 8601 timestamp string
+ * (YYYY-MM-DDTHH:MM:SS). Returns "N/A" if the timestamp is zero
+ * or does not fit in time_t.
+ */
+#include <time.h>
+#include <linux/time_types.h>
+#include "format_timespec.h"
+
+const char *format_timespec(const struct __kernel_timespec *ts)
+{
+	static char buffer[32];
+	struct tm tm_info;
+	time_t time_sec;
+
+	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
+		return "N/A";
+
+	/*
+	 * On 32-bit platforms time_t is 32-bit and cannot represent
+	 * dates beyond Y2038.  The kernel timestamp is always 64-bit,
+	 * so reject values that would overflow.
+	 */
+	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
+	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
+		return "N/A";
+
+	time_sec = ts->tv_sec;
+
+	if (!localtime_r(&time_sec, &tm_info))
+		return "N/A";
+
+	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
+
+	return buffer;
+}
diff --git a/tools/accounting/format_timespec.h b/tools/accounting/format_timespec.h
new file mode 100644
index 000000000000..960496ebf5c2
--- /dev/null
+++ b/tools/accounting/format_timespec.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef FORMAT_TIMESPEC_H
+#define FORMAT_TIMESPEC_H
+
+#include <linux/time_types.h>
+
+const char *format_timespec(const struct __kernel_timespec *ts);
+
+#endif
diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 6ac30d4f96f7..d3193f670d89 100644
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -30,6 +30,8 @@
 #include <linux/taskstats.h>
 #include <linux/cgroupstats.h>

+#include "format_timespec.h"
+
 /*
  * Generic macros for dealing with netlink sockets. Might be duplicated
  * elsewhere. It is recommended that commercial grade applications use
@@ -221,36 +223,6 @@ static int get_family_id(int sd)
 #define average_ms(t, c) (t / 1000000ULL / (c ? c : 1))
 #define delay_ms(t) (t / 1000000ULL)

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DD HH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	struct tm tm_info;
-	__kernel_time_t time_sec;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation on 32-bit platforms */
-	if (sizeof(time_sec) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_sec) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = ts->tv_sec;
-
-	/* Use thread-safe localtime_r */
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
-
-	return buffer;
-}
-
 /*
  * Version compatibility note:
  * Field availability depends on taskstats version (t->version),
diff --git a/tools/include/uapi/linux/time_types.h b/tools/include/uapi/linux/time_types.h
new file mode 100644
index 000000000000..90347781af54
--- /dev/null
+++ b/tools/include/uapi/linux/time_types.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _TOOLS_UAPI_LINUX_TIME_TYPES_H
+#define _TOOLS_UAPI_LINUX_TIME_TYPES_H
+
+#include <linux/types.h>
+
+/*
+ * Copied from include/uapi/linux/time_types.h
+ *
+ * __kernel_time64_t is always 'long long' on all architectures.
+ * __kernel_long_t / __kernel_old_time_t is always 'long' on Linux.
+ * The concrete types are used here to avoid pulling in arch-specific
+ * kernel-private type definitions.
+ */
+
+struct __kernel_timespec {
+	long long	tv_sec;
+	long long	tv_nsec;
+};
+
+struct __kernel_itimerspec {
+	struct __kernel_timespec it_interval;
+	struct __kernel_timespec it_value;
+};
+
+struct __kernel_old_timeval {
+	long		tv_sec;
+	long		tv_usec;
+};
+
+struct __kernel_old_timespec {
+	long		tv_sec;
+	long		tv_nsec;
+};
+
+struct __kernel_old_itimerval {
+	struct __kernel_old_timeval it_interval;
+	struct __kernel_old_timeval it_value;
+};
+
+struct __kernel_sock_timeval {
+	__s64 tv_sec;
+	__s64 tv_usec;
+};
+
+#endif /* _TOOLS_UAPI_LINUX_TIME_TYPES_H */
-- 
2.27.0

[PATCH v3 0/3] tools/accounting: refactor delay fields and share format_timespec()

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

- Convert per-field delay members in struct task_info to an array indexed
  by enum delay_type, eliminating offsetof() pointer arithmetic.

- Factor out a common format_timespec() implementation shared by getdelays
  and delaytop, using strftime for cleaner timestamp formatting.

- Replace the complex sizeof/ULL/shift Y2038 guard with a direct narrowing
  truncation check ((long long)time_sec != ts->tv_sec).

Change Log
==========
v2->v3:
update patch 2/3 and 3/3 according to the suggestion:
https://sashiko.dev/#/patchset/20260715124740929HC7tDDb2SK3kRxbuPruHd@zte.com.cn

1. tools/include/uapi/linux/time_types.h: use __kernel_long_t instead of
long to fix ABI mismatch on x32
2. tools/accounting: add nla_len < NLA_HDRLEN checks in netlink attribute
parsing loops to prevent infinite loop on malformed messages

v1->v2:
Only update patch 2/3 according to the suggestion:
https://sashiko.dev/#/patchset/20260711173112482SCQEM08VED2PT1pxUYOXk@zte.com.cn

1. tools/include/uapi/linux/time_types.h: expand stub to full set of
  6 structs from kernel UAPI to avoid shadowing system header
2. tools/accounting/Makefile: add $(LDFLAGS), $(LDLIBS), $(CPPFLAGS)
  to restore compatibility with standard build variables

Wang Yaxin (3):
  delaytop: refactor repetitive delay fields into array with enum
  tools/accounting: factor out shared format_timespec() implementation
  tools/accounting: simplify 32-bit time_t overflow check in
    format_timespec()

 tools/accounting/Makefile             |  12 +-
 tools/accounting/delaytop.c           | 265 ++++++++++----------------
 tools/accounting/format_timespec.c    |  37 ++++
 tools/accounting/format_timespec.h    |   9 +
 tools/accounting/getdelays.c          |  36 +---
 tools/include/uapi/linux/time_types.h |  49 +++++
 6 files changed, 208 insertions(+), 200 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

-- 
2.27.0

[PATCH 2/3] tools/accounting: factor out shared format_timespec() implementation

[wang.yaxin]

From: Wang Yaxin <wang.yaxin@zte.com.cn>

The same __kernel_timespec formatting logic existed independently in
both getdelays.c and delaytop.c with minor differences (strftime vs
snprintf, __kernel_time64_t vs time_t).

Create a shared format_timespec.c/h with a canonical implementation
(strftime + time_t), remove the static copies from both files, and
link both programs against the common object.

Also simplify the Makefile with a pattern rule for %.o and a static
pattern rule for the two programs that need format_timespec.o.

Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
---
 tools/accounting/Makefile             | 12 ++++++-
 tools/accounting/delaytop.c           | 39 ++-------------------
 tools/accounting/format_timespec.c    | 39 +++++++++++++++++++++
 tools/accounting/format_timespec.h    |  9 +++++
 tools/accounting/getdelays.c          | 32 ++---------------
 tools/include/uapi/linux/time_types.h | 49 +++++++++++++++++++++++++++
 6 files changed, 113 insertions(+), 67 deletions(-)
 create mode 100644 tools/accounting/format_timespec.c
 create mode 100644 tools/accounting/format_timespec.h
 create mode 100644 tools/include/uapi/linux/time_types.h

diff --git a/tools/accounting/Makefile b/tools/accounting/Makefile
index 007c0bb8cbbb..5224e03f5e94 100644
--- a/tools/accounting/Makefile
+++ b/tools/accounting/Makefile
@@ -3,8 +3,18 @@ CC := $(CROSS_COMPILE)gcc
 CFLAGS := -I../include/uapi/

 PROGS := getdelays procacct delaytop
+OBJS := format_timespec.o

 all: $(PROGS)

+getdelays delaytop: %: %.o $(OBJS)
+	$(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+procacct: procacct.o
+	$(CC) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
+%.o: %.c
+	$(CC) $(CPPFLAGS) $(CFLAGS) -c -o $@ $<
+
 clean:
-	rm -fr $(PROGS)
+	rm -fr $(PROGS) *.o
diff --git a/tools/accounting/delaytop.c b/tools/accounting/delaytop.c
index f1d26ff98792..1144ca325447 100644
--- a/tools/accounting/delaytop.c
+++ b/tools/accounting/delaytop.c
@@ -44,6 +44,8 @@
 #include <linux/cgroupstats.h>
 #include <stddef.h>

+#include "format_timespec.h"
+
 #define PSI_PATH	"/proc/pressure"
 #define PSI_CPU_PATH	"/proc/pressure/cpu"
 #define PSI_MEMORY_PATH	"/proc/pressure/memory"
@@ -817,41 +819,6 @@ static double average_ms(unsigned long long total, unsigned long long count)
 	return (double)total / 1000000.0 / count;
 }

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DDTHH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_kernel_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	time_t time_sec;
-	struct tm tm_info;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation: check if timestamp fits in time_t on 32-bit platforms */
-	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = (time_t)ts->tv_sec;
-
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d",
-		tm_info.tm_year + 1900,
-		tm_info.tm_mon + 1,
-		tm_info.tm_mday,
-		tm_info.tm_hour,
-		tm_info.tm_min,
-		tm_info.tm_sec);
-
-	return buffer;
-}
-
 /* Comparison function for sorting tasks */
 static int compare_tasks(const void *a, const void *b)
 {
@@ -1133,7 +1100,7 @@ static void display_results(int psi_ret)
 					&max_ms, &max_ts);

 			suc &= BOOL_FPRINT(out, "%12.2f %12.2f %20s\n",
-				avg_ms, max_ms, format_kernel_timespec(&max_ts));
+				avg_ms, max_ms, format_timespec(&max_ts));
 		} else if (cfg.display_mode == MODE_MEMVERBOSE) {
 			suc &= BOOL_FPRINT(out, DELAY_FMT_MEMVERBOSE,
 				TASK_AVG(tasks[i], MEM),
diff --git a/tools/accounting/format_timespec.c b/tools/accounting/format_timespec.c
new file mode 100644
index 000000000000..1dba50cac895
--- /dev/null
+++ b/tools/accounting/format_timespec.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shared __kernel_timespec formatting for tools/accounting/
+ *
+ * Formats a __kernel_timespec to an ISO 8601 timestamp string
+ * (YYYY-MM-DDTHH:MM:SS). Returns "N/A" if the timestamp is zero
+ * or does not fit in time_t.
+ */
+#include <time.h>
+#include <linux/time_types.h>
+#include "format_timespec.h"
+
+const char *format_timespec(const struct __kernel_timespec *ts)
+{
+	static char buffer[32];
+	struct tm tm_info;
+	time_t time_sec;
+
+	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
+		return "N/A";
+
+	/*
+	 * On 32-bit platforms time_t is 32-bit and cannot represent
+	 * dates beyond Y2038.  The kernel timestamp is always 64-bit,
+	 * so reject values that would overflow.
+	 */
+	if (sizeof(time_t) < sizeof(ts->tv_sec) &&
+	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_t) * 8 - 1)) - 1))
+		return "N/A";
+
+	time_sec = ts->tv_sec;
+
+	if (!localtime_r(&time_sec, &tm_info))
+		return "N/A";
+
+	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
+
+	return buffer;
+}
diff --git a/tools/accounting/format_timespec.h b/tools/accounting/format_timespec.h
new file mode 100644
index 000000000000..960496ebf5c2
--- /dev/null
+++ b/tools/accounting/format_timespec.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef FORMAT_TIMESPEC_H
+#define FORMAT_TIMESPEC_H
+
+#include <linux/time_types.h>
+
+const char *format_timespec(const struct __kernel_timespec *ts);
+
+#endif
diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 6ac30d4f96f7..d3193f670d89 100644
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -30,6 +30,8 @@
 #include <linux/taskstats.h>
 #include <linux/cgroupstats.h>

+#include "format_timespec.h"
+
 /*
  * Generic macros for dealing with netlink sockets. Might be duplicated
  * elsewhere. It is recommended that commercial grade applications use
@@ -221,36 +223,6 @@ static int get_family_id(int sd)
 #define average_ms(t, c) (t / 1000000ULL / (c ? c : 1))
 #define delay_ms(t) (t / 1000000ULL)

-/*
- * Format __kernel_timespec to human readable string (YYYY-MM-DD HH:MM:SS)
- * Returns formatted string or "N/A" if timestamp is zero
- */
-static const char *format_timespec(struct __kernel_timespec *ts)
-{
-	static char buffer[32];
-	struct tm tm_info;
-	__kernel_time_t time_sec;
-
-	/* Check if timestamp is zero (not set) */
-	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
-		return "N/A";
-
-	/* Avoid Y2038 truncation on 32-bit platforms */
-	if (sizeof(time_sec) < sizeof(ts->tv_sec) &&
-	    ts->tv_sec > (__u64)((1ULL << (sizeof(time_sec) * 8 - 1)) - 1))
-		return "N/A";
-
-	time_sec = ts->tv_sec;
-
-	/* Use thread-safe localtime_r */
-	if (localtime_r(&time_sec, &tm_info) == NULL)
-		return "N/A";
-
-	strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
-
-	return buffer;
-}
-
 /*
  * Version compatibility note:
  * Field availability depends on taskstats version (t->version),
diff --git a/tools/include/uapi/linux/time_types.h b/tools/include/uapi/linux/time_types.h
new file mode 100644
index 000000000000..1b9d576d7cc5
--- /dev/null
+++ b/tools/include/uapi/linux/time_types.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _TOOLS_UAPI_LINUX_TIME_TYPES_H
+#define _TOOLS_UAPI_LINUX_TIME_TYPES_H
+
+#include <linux/types.h>
+#include <asm/posix_types.h>
+
+/*
+ * Copied from include/uapi/linux/time_types.h
+ *
+ * Uses the arch-dependent __kernel_long_t rather than a hardcoded
+ * 'long' so that x32 (ILP32 on x86_64), where the kernel defines
+ * __kernel_long_t as 'long long', gets the correct struct layout.
+ *
+ * __kernel_long_t is provided by <asm/posix_types.h> - included
+ * below via <linux/types.h> on most systems, or directly here.
+ */
+
+struct __kernel_timespec {
+	long long	tv_sec;
+	long long	tv_nsec;
+};
+
+struct __kernel_itimerspec {
+	struct __kernel_timespec it_interval;
+	struct __kernel_timespec it_value;
+};
+
+struct __kernel_old_timeval {
+	__kernel_long_t		tv_sec;
+	__kernel_long_t		tv_usec;
+};
+
+struct __kernel_old_timespec {
+	__kernel_long_t		tv_sec;
+	long			tv_nsec;
+};
+
+struct __kernel_old_itimerval {
+	struct __kernel_old_timeval it_interval;
+	struct __kernel_old_timeval it_value;
+};
+
+struct __kernel_sock_timeval {
+	__s64 tv_sec;
+	__s64 tv_usec;
+};
+
+#endif /* _TOOLS_UAPI_LINUX_TIME_TYPES_H */
-- 
2.27.0

Re: [PATCH 2/3] tools/accounting: factor out shared format_timespec() implementation

[xu.xin16]

> From: Wang Yaxin <wang.yaxin@zte.com.cn>
> 
> The same __kernel_timespec formatting logic existed independently in
> both getdelays.c and delaytop.c with minor differences (strftime vs
> snprintf, __kernel_time64_t vs time_t).
> 
> Create a shared format_timespec.c/h with a canonical implementation
> (strftime + time_t), remove the static copies from both files, and
> link both programs against the common object.
> 
> Also simplify the Makefile with a pattern rule for %.o and a static
> pattern rule for the two programs that need format_timespec.o.
> 
> Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>

Acked-by: Xu Xin <xu.xin16@zte.com.cn>