[for-next][PATCH 0/4] tracing: A few more changes for 4.13

[for-next][PATCH 0/4] tracing: A few more changes for 4.13

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
for-next

Head SHA1: 29b1a8ad7df4528b862a79e3d5fb0936f4d199c7


Joel Fernandes (3):
      tracing: Treat recording comm for idle task as a success
      tracing: Treat recording tgid for idle task as a success
      tracing: Attempt to record other information even if some fail

Michael Sartain (1):
      tracing: Add saved_tgids file to show cached pid to tgid mappings

----
 kernel/trace/trace.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 107 insertions(+), 10 deletions(-)

[for-next][PATCH 1/4] tracing: Add saved_tgids file to show cached pid to tgid mappings

[Steven Rostedt]

[-- Attachment #1: 0001-tracing-Add-saved_tgids-file-to-show-cached-pid-to-t.patch --]
[-- Type: text/plain, Size: 2833 bytes --]

From: Michael Sartain <mikesart@fastmail.com>

Export the cached pid / tgid mappings in debugfs tracing saved_tgids file.
This allows user apps to translate the pids from a trace to their respective
thread group.

Example saved_tgids file with pid / tgid values separated by ' ':

  # cat saved_tgids
  1048 1048
  1047 1047
  7 7
  1049 1047
  1054 1047
  1053 1047

Link: http://lkml.kernel.org/r/20170630004023.064965233@goodmis.org
Link: http://lkml.kernel.org/r/20170706040713.unwkumbta5menygi@mikesart-cos

Reviewed-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Michael Sartain <mikesart@fastmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 00e2e4169b1e..f079a8ca1117 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4688,6 +4688,76 @@ static const struct file_operations tracing_readme_fops = {
 	.llseek		= generic_file_llseek,
 };
 
+static void *saved_tgids_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	int *ptr = v;
+
+	if (*pos || m->count)
+		ptr++;
+
+	(*pos)++;
+
+	for (; ptr <= &tgid_map[PID_MAX_DEFAULT]; ptr++) {
+		if (trace_find_tgid(*ptr))
+			return ptr;
+	}
+
+	return NULL;
+}
+
+static void *saved_tgids_start(struct seq_file *m, loff_t *pos)
+{
+	void *v;
+	loff_t l = 0;
+
+	if (!tgid_map)
+		return NULL;
+
+	v = &tgid_map[0];
+	while (l <= *pos) {
+		v = saved_tgids_next(m, v, &l);
+		if (!v)
+			return NULL;
+	}
+
+	return v;
+}
+
+static void saved_tgids_stop(struct seq_file *m, void *v)
+{
+}
+
+static int saved_tgids_show(struct seq_file *m, void *v)
+{
+	int pid = (int *)v - tgid_map;
+
+	seq_printf(m, "%d %d\n", pid, trace_find_tgid(pid));
+	return 0;
+}
+
+static const struct seq_operations tracing_saved_tgids_seq_ops = {
+	.start		= saved_tgids_start,
+	.stop		= saved_tgids_stop,
+	.next		= saved_tgids_next,
+	.show		= saved_tgids_show,
+};
+
+static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)
+{
+	if (tracing_disabled)
+		return -ENODEV;
+
+	return seq_open(filp, &tracing_saved_tgids_seq_ops);
+}
+
+
+static const struct file_operations tracing_saved_tgids_fops = {
+	.open		= tracing_saved_tgids_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
 static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	unsigned int *ptr = v;
@@ -7920,6 +7990,9 @@ static __init int tracer_init_tracefs(void)
 	trace_create_file("saved_cmdlines_size", 0644, d_tracer,
 			  NULL, &tracing_saved_cmdlines_size_fops);
 
+	trace_create_file("saved_tgids", 0444, d_tracer,
+			NULL, &tracing_saved_tgids_fops);
+
 	trace_eval_init();
 
 	trace_create_eval_file(d_tracer);
-- 
2.10.2

[for-next][PATCH 2/4] tracing: Treat recording comm for idle task as a success

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-Treat-recording-comm-for-idle-task-as-a-succ.patch --]
[-- Type: text/plain, Size: 1085 bytes --]

From: Joel Fernandes <joelaf@google.com>

Currently we stop recording comm for non-idle tasks when switching from/to idle
task since we treat that as a record failure. Fix that by treat recording of
comm for idle task as a success.

Link: http://lkml.kernel.org/r/20170706230023.17942-1-joelaf@google.com

Cc: kernel-team@android.com
Cc: Ingo Molnar <mingo@redhat.com>
Reported-by: Michael Sartain <mikesart@gmail.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f079a8ca1117..6722d86f2af5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1916,7 +1916,11 @@ static int trace_save_cmdline(struct task_struct *tsk)
 {
 	unsigned pid, idx;
 
-	if (!tsk->pid || unlikely(tsk->pid > PID_MAX_DEFAULT))
+	/* treat recording of idle task as a success */
+	if (!tsk->pid)
+		return 1;
+
+	if (unlikely(tsk->pid > PID_MAX_DEFAULT))
 		return 0;
 
 	/*
-- 
2.10.2

[for-next][PATCH 3/4] tracing: Treat recording tgid for idle task as a success

[Steven Rostedt]

[-- Attachment #1: 0003-tracing-Treat-recording-tgid-for-idle-task-as-a-succ.patch --]
[-- Type: text/plain, Size: 1146 bytes --]

From: Joel Fernandes <joelaf@google.com>

Currently we stop recording tgid for non-idle tasks when switching from/to idle
task since we treat that as a record failure. Fix that by treat recording of
tgid for idle task as a success.

Link: http://lkml.kernel.org/r/20170706230023.17942-2-joelaf@google.com

Cc: kernel-team@android.com
Cc: Ingo Molnar <mingo@redhat.com>
Reported-by: Michael Sartain <mikesart@gmail.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6722d86f2af5..aee11e3a394f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2006,7 +2006,11 @@ int trace_find_tgid(int pid)
 
 static int trace_save_tgid(struct task_struct *tsk)
 {
-	if (unlikely(!tgid_map || !tsk->pid || tsk->pid > PID_MAX_DEFAULT))
+	/* treat recording of idle task as a success */
+	if (!tsk->pid)
+		return 1;
+
+	if (unlikely(!tgid_map || tsk->pid > PID_MAX_DEFAULT))
 		return 0;
 
 	tgid_map[tsk->pid] = tsk->tgid;
-- 
2.10.2

[for-next][PATCH 4/4] tracing: Attempt to record other information even if some fail

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-Attempt-to-record-other-information-even-if-.patch --]
[-- Type: text/plain, Size: 2618 bytes --]

From: Joel Fernandes <joelaf@google.com>

In recent patches where we record comm and tgid at the same time, we skip
continuing to record if any fail. Fix that by trying to record as many things
as we can even if some couldn't be recorded. If any information isn't recorded,
then we don't set trace_taskinfo_save as before.

Link: http://lkml.kernel.org/r/20170706230023.17942-3-joelaf@google.com

Cc: kernel-team@android.com
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index aee11e3a394f..92af8fd1429b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2037,11 +2037,20 @@ static bool tracing_record_taskinfo_skip(int flags)
  */
 void tracing_record_taskinfo(struct task_struct *task, int flags)
 {
+	bool done;
+
 	if (tracing_record_taskinfo_skip(flags))
 		return;
-	if ((flags & TRACE_RECORD_CMDLINE) && !trace_save_cmdline(task))
-		return;
-	if ((flags & TRACE_RECORD_TGID) && !trace_save_tgid(task))
+
+	/*
+	 * Record as much task information as possible. If some fail, continue
+	 * to try to record the others.
+	 */
+	done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);
+
+	/* If recording any information failed, retry again soon. */
+	if (!done)
 		return;
 
 	__this_cpu_write(trace_taskinfo_save, false);
@@ -2058,15 +2067,22 @@ void tracing_record_taskinfo(struct task_struct *task, int flags)
 void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
 					  struct task_struct *next, int flags)
 {
+	bool done;
+
 	if (tracing_record_taskinfo_skip(flags))
 		return;
 
-	if ((flags & TRACE_RECORD_CMDLINE) &&
-	    (!trace_save_cmdline(prev) || !trace_save_cmdline(next)))
-		return;
+	/*
+	 * Record as much task information as possible. If some fail, continue
+	 * to try to record the others.
+	 */
+	done  = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
+	done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
+	done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);
 
-	if ((flags & TRACE_RECORD_TGID) &&
-	    (!trace_save_tgid(prev) || !trace_save_tgid(next)))
+	/* If recording any information failed, retry again soon. */
+	if (!done)
 		return;
 
 	__this_cpu_write(trace_taskinfo_save, false);
-- 
2.10.2