[for-next][PATCH 0/4] tracing: Some more updates for 4.15

[for-next][PATCH 0/4] tracing: Some more updates for 4.15

[Steven Rostedt]

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

Head SHA1: f40a37cb4916f17806b8a89d8eb76f6943c69189


Arnd Bergmann (1):
      tracing: mark trace_test_buffer as __maybe_unused

Steven Rostedt (VMware) (3):
      printk: Remove superfluous memory barriers from printk_safe
      tracing/xen: Hide events that are not used when X86_PAE is not defined
      tracing, memcg, vmscan: Hide trace events when not in use

----
 include/trace/events/vmscan.h |  4 ++++
 include/trace/events/xen.h    | 35 +++++++++++++++++++----------------
 kernel/printk/printk_safe.c   | 15 ++++++++-------
 kernel/trace/trace_selftest.c |  2 +-
 4 files changed, 32 insertions(+), 24 deletions(-)

[for-next][PATCH 1/4] printk: Remove superfluous memory barriers from printk_safe

[Steven Rostedt]

[-- Attachment #1: 0001-printk-Remove-superfluous-memory-barriers-from-print.patch --]
[-- Type: text/plain, Size: 2032 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

The variable printk_safe_irq_ready is set and never cleared at system
boot up, when there's only one CPU active. It is set before other
CPUs come on line. Also, it is extremely unlikely that an NMI would
trigger this early in boot up (which I wonder why we even have this
variable at all).

Also mark the printk_safe_irq_ready as read mostly, as it is set at
system boot up, and never touched again.

Link: http://lkml.kernel.org/r/20171011124647.7781f98f@gandalf.local.home

Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/printk/printk_safe.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 3cdaeaef9ce1..724d9292d4b9 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -39,7 +39,7 @@
  * There are situations when we want to make sure that all buffers
  * were handled or when IRQs are blocked.
  */
-static int printk_safe_irq_ready;
+static int printk_safe_irq_ready __read_mostly;
 
 #define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) -	\
 				sizeof(atomic_t) -			\
@@ -63,11 +63,8 @@ static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);
 /* Get flushed in a more safe context. */
 static void queue_flush_work(struct printk_safe_seq_buf *s)
 {
-	if (printk_safe_irq_ready) {
-		/* Make sure that IRQ work is really initialized. */
-		smp_rmb();
+	if (printk_safe_irq_ready)
 		irq_work_queue(&s->work);
-	}
 }
 
 /*
@@ -398,8 +395,12 @@ void __init printk_safe_init(void)
 #endif
 	}
 
-	/* Make sure that IRQ works are initialized before enabling. */
-	smp_wmb();
+	/*
+	 * In the highly unlikely event that a NMI were to trigger at
+	 * this moment. Make sure IRQ work is set up before this
+	 * variable is set.
+	 */
+	barrier();
 	printk_safe_irq_ready = 1;
 
 	/* Flush pending messages that did not have scheduled IRQ works. */
-- 
2.13.2

[for-next][PATCH 2/4] tracing: mark trace_test_buffer as __maybe_unused

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-mark-trace_test_buffer-as-__maybe_unused.patch --]
[-- Type: text/plain, Size: 1454 bytes --]

From: Arnd Bergmann <arnd@arndb.de>

After trace_selftest_startup_sched_switch is removed, trace_test_buffer()
is only used sometimes, leading to this warning:

kernel/trace/trace_selftest.c:62:12: error: 'trace_test_buffer' defined but not used [-Werror=unused-function]

There is no simple #ifdef condition that captures well whether the
function is in fact used or not, so marking it as __maybe_unused is
probably the best way to shut up the warning. The function will then
be silently dropped when there is no user.

Link: http://lkml.kernel.org/r/20171013142227.1273469-1-arnd@arndb.de

Fixes: d8c4deee6dc6 ("tracing: Remove obsolete sched_switch tracer selftest")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_selftest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 364f78abdf47..eb9ba5c1ba40 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -59,7 +59,7 @@ static int trace_test_buffer_cpu(struct trace_buffer *buf, int cpu)
  * Test the trace buffer to see if all the elements
  * are still sane.
  */
-static int trace_test_buffer(struct trace_buffer *buf, unsigned long *count)
+static int __maybe_unused trace_test_buffer(struct trace_buffer *buf, unsigned long *count)
 {
 	unsigned long flags, cnt = 0;
 	int cpu, ret = 0;
-- 
2.13.2

[for-next][PATCH 3/4] tracing/xen: Hide events that are not used when X86_PAE is not defined

[Steven Rostedt]

[-- Attachment #1: 0003-tracing-xen-Hide-events-that-are-not-used-when-X86_P.patch --]
[-- Type: text/plain, Size: 2805 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

TRACE_EVENTS() take up memory. If they are defined but not used, then
they simply waste space. If their use case is behind a define, then the
trace events should be as well.

The trace events xen_mmu_set_pte_atomic, xen_mmu_pte_clear, and
xen_mmu_pmd_clear are not used when CONFIG_X86_PAE is not defined.

Link: http://lkml.kernel.org/r/20171010191256.3d6d72cb@gandalf.local.home

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/trace/events/xen.h | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
index 1b4fed72f573..6118d82334ec 100644
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -147,7 +147,6 @@ DECLARE_EVENT_CLASS(xen_mmu__set_pte,
 		     TP_ARGS(ptep, pteval))
 
 DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte);
-DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte_atomic);
 
 TRACE_EVENT(xen_mmu_set_pte_at,
 	    TP_PROTO(struct mm_struct *mm, unsigned long addr,
@@ -169,21 +168,6 @@ TRACE_EVENT(xen_mmu_set_pte_at,
 		      (int)sizeof(pteval_t) * 2, (unsigned long long)__entry->pteval)
 	);
 
-TRACE_EVENT(xen_mmu_pte_clear,
-	    TP_PROTO(struct mm_struct *mm, unsigned long addr, pte_t *ptep),
-	    TP_ARGS(mm, addr, ptep),
-	    TP_STRUCT__entry(
-		    __field(struct mm_struct *, mm)
-		    __field(unsigned long, addr)
-		    __field(pte_t *, ptep)
-		    ),
-	    TP_fast_assign(__entry->mm = mm;
-			   __entry->addr = addr;
-			   __entry->ptep = ptep),
-	    TP_printk("mm %p addr %lx ptep %p",
-		      __entry->mm, __entry->addr, __entry->ptep)
-	);
-
 TRACE_DEFINE_SIZEOF(pmdval_t);
 
 TRACE_EVENT(xen_mmu_set_pmd,
@@ -201,6 +185,24 @@ TRACE_EVENT(xen_mmu_set_pmd,
 		      (int)sizeof(pmdval_t) * 2, (unsigned long long)__entry->pmdval)
 	);
 
+#ifdef CONFIG_X86_PAE
+DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte_atomic);
+
+TRACE_EVENT(xen_mmu_pte_clear,
+	    TP_PROTO(struct mm_struct *mm, unsigned long addr, pte_t *ptep),
+	    TP_ARGS(mm, addr, ptep),
+	    TP_STRUCT__entry(
+		    __field(struct mm_struct *, mm)
+		    __field(unsigned long, addr)
+		    __field(pte_t *, ptep)
+		    ),
+	    TP_fast_assign(__entry->mm = mm;
+			   __entry->addr = addr;
+			   __entry->ptep = ptep),
+	    TP_printk("mm %p addr %lx ptep %p",
+		      __entry->mm, __entry->addr, __entry->ptep)
+	);
+
 TRACE_EVENT(xen_mmu_pmd_clear,
 	    TP_PROTO(pmd_t *pmdp),
 	    TP_ARGS(pmdp),
@@ -210,6 +212,7 @@ TRACE_EVENT(xen_mmu_pmd_clear,
 	    TP_fast_assign(__entry->pmdp = pmdp),
 	    TP_printk("pmdp %p", __entry->pmdp)
 	);
+#endif
 
 #if CONFIG_PGTABLE_LEVELS >= 4
 
-- 
2.13.2

[for-next][PATCH 4/4] tracing, memcg, vmscan: Hide trace events when not in use

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-memcg-vmscan-Hide-trace-events-when-not-in-u.patch --]
[-- Type: text/plain, Size: 2064 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

When trace events are defined but not used they still create data
structures and functions for their use, even though nothing may be
using them.

The trace events mm_vmscan_memcg_reclaim_begin,
mm_vmscan_memcg_softlimit_reclaim_begin, mm_vmscan_memcg_reclaim_end,
and mm_vmscan_memcg_softlimit_reclaim_end are not used if CONFIG_MEMCG
is not defined. Do not create these trace events unless CONFIG_MEMCG is
defined.

Link: http://lkml.kernel.org/r/20171012184632.2bd247cd@gandalf.local.home

Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/trace/events/vmscan.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index 27e8a5c77579..cde5fea0a179 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -133,6 +133,7 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_direct_reclaim_b
 	TP_ARGS(order, may_writepage, gfp_flags, classzone_idx)
 );
 
+#ifdef CONFIG_MEMCG
 DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_memcg_reclaim_begin,
 
 	TP_PROTO(int order, int may_writepage, gfp_t gfp_flags, int classzone_idx),
@@ -146,6 +147,7 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_begin_template, mm_vmscan_memcg_softlimit_
 
 	TP_ARGS(order, may_writepage, gfp_flags, classzone_idx)
 );
+#endif /* CONFIG_MEMCG */
 
 DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_end_template,
 
@@ -171,6 +173,7 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_direct_reclaim_end
 	TP_ARGS(nr_reclaimed)
 );
 
+#ifdef CONFIG_MEMCG
 DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_reclaim_end,
 
 	TP_PROTO(unsigned long nr_reclaimed),
@@ -184,6 +187,7 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_softlimit_re
 
 	TP_ARGS(nr_reclaimed)
 );
+#endif /* CONFIG_MEMCG */
 
 TRACE_EVENT(mm_shrink_slab_start,
 	TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
-- 
2.13.2