[PATCH 4/5] mm, oom_reaper: report success/failure

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

Inform about the successful/failed oom_reaper attempts and dump all the
held locks to tell us more who is blocking the progress.

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 mm/oom_kill.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8e345126d73e..b87acdca2a41 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -420,6 +420,7 @@ static struct task_struct *oom_reaper_th;
 static struct task_struct *task_to_reap;
 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
 
+#define K(x) ((x) << (PAGE_SHIFT-10))
 static bool __oom_reap_task(struct task_struct *tsk)
 {
 	struct mmu_gather tlb;
@@ -476,6 +477,11 @@ static bool __oom_reap_task(struct task_struct *tsk)
 		}
 	}
 	tlb_finish_mmu(&tlb, 0, -1);
+	pr_info("oom_reaper: reaped process :%d (%s) anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lulB\n",
+			task_pid_nr(tsk), tsk->comm,
+			K(get_mm_counter(mm, MM_ANONPAGES)),
+			K(get_mm_counter(mm, MM_FILEPAGES)),
+			K(get_mm_counter(mm, MM_SHMEMPAGES)));
 	up_read(&mm->mmap_sem);
 
 	/*
@@ -492,14 +498,21 @@ static bool __oom_reap_task(struct task_struct *tsk)
 	return ret;
 }
 
+#define MAX_OOM_REAP_RETRIES 10
 static void oom_reap_task(struct task_struct *tsk)
 {
 	int attempts = 0;
 
 	/* Retry the down_read_trylock(mmap_sem) a few times */
-	while (attempts++ < 10 && !__oom_reap_task(tsk))
+	while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task(tsk))
 		schedule_timeout_idle(HZ/10);
 
+	if (attempts > MAX_OOM_REAP_RETRIES) {
+		pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
+				task_pid_nr(tsk), tsk->comm);
+		debug_show_all_locks();
+	}
+
 	/* Drop a reference taken by wake_oom_reaper */
 	put_task_struct(tsk);
 }
@@ -646,7 +659,6 @@ static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
 	return false;
 }
 
-#define K(x) ((x) << (PAGE_SHIFT-10))
 /*
  * Must be called while holding a reference to p, which will be released upon
  * returning.
-- 
2.7.0