tracepoint: add tracepoints for debugging oom_score_adj

oom_score_adj is used for guarding processes from OOM-Killer.  One of
problem is that it's inherited at fork().  When a daemon set oom_score_adj
and make children, it's hard to know where the value is set.

This patch adds some tracepoints useful for debugging. This patch adds
3 trace points.
  - creating new task
  - renaming a task (exec)
  - set oom_score_adj

To debug, users need to enable some trace pointer. Maybe filtering is useful as

# EVENT=/sys/kernel/debug/tracing/events/task/
# echo "oom_score_adj != 0" > $EVENT/task_newtask/filter
# echo "oom_score_adj != 0" > $EVENT/task_rename/filter
# echo 1 > $EVENT/enable
# EVENT=/sys/kernel/debug/tracing/events/oom/
# echo 1 > $EVENT/enable

output will be like this.
# grep oom /sys/kernel/debug/tracing/trace
bash-7699  [007] d..3  5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000
bash-7699  [007] ...1  5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000
ls-7729  [003] ...2  5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000
bash-7699  [002] ...1  5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000
grep-7730  [007] ...2  5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 7 insertions, 0 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 3f64b9f26e7d..aeb135c7ff5c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -59,6 +59,8 @@
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/tlb.h>
+
+#include <trace/events/task.h>
 #include "internal.h"
 
 int core_uses_pid;
@@ -1054,6 +1056,8 @@ void set_task_comm(struct task_struct *tsk, char *buf)
 {
         task_lock(tsk);
 
+        trace_task_rename(tsk, buf);
+
         /*
          * Threads may access current->comm without holding
          * the task lock, so write the string carefully.
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a1dddda999f2..1aab5fe05a1b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -86,6 +86,7 @@
 #ifdef CONFIG_HARDWALL
 #include <asm/hardwall.h>
 #endif
+#include <trace/events/oom.h>
 #include "internal.h"
 
 /* NOTE:
@@ -1010,6 +1011,7 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
         else
                 task->signal->oom_score_adj = (oom_adjust * OOM_SCORE_ADJ_MAX) /
                                                                 -OOM_DISABLE;
+        trace_oom_score_adj_update(task);
 err_sighand:
         unlock_task_sighand(task, &flags);
 err_task_lock:
@@ -1097,6 +1099,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
         task->signal->oom_score_adj = oom_score_adj;
         if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
                 task->signal->oom_score_adj_min = oom_score_adj;
+        trace_oom_score_adj_update(task);
         /*
          * Scale /proc/pid/oom_adj appropriately ensuring that OOM_DISABLE is
          * always attainable.