From 5d90ba12b936cea4a0e8028ebe69703e589a3b59 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Arkadiusz=20Mi=C5=9Bkiewicz?= Date: Sat, 26 Jan 2019 13:02:58 +0100 Subject: [PATCH] - rel 2; fix pids.current counting --- kernel-small_fixes.patch | 110 +++++++++++++++++++++++++++++++++++++++ kernel.spec | 2 +- 2 files changed, 111 insertions(+), 1 deletion(-) diff --git a/kernel-small_fixes.patch b/kernel-small_fixes.patch index 63bd4794..19610274 100644 --- a/kernel-small_fixes.patch +++ b/kernel-small_fixes.patch @@ -162,3 +162,113 @@ index 76c92e31afc0..abb5d382f64d 100644 -- cgit 1.2-0.3.lf.el7 +From 48744b6339cf649a69b55997e138c17df1ecc897 Mon Sep 17 00:00:00 2001 +From: Tetsuo Handa +Date: Sat, 26 Jan 2019 20:00:51 +0900 +Subject: [PATCH] oom, oom_reaper: do not enqueue same task twice + +Arkadiusz reported that enabling memcg's group oom killing causes +strange memcg statistics where there is no task in a memcg despite +the number of tasks in that memcg is not 0. It turned out that there +is a bug in wake_oom_reaper() which allows enqueuing same task twice +which makes impossible to decrease the number of tasks in that memcg +due to a refcount leak. + +This bug existed since the OOM reaper became invokable from +task_will_free_mem(current) path in out_of_memory() in Linux 4.7, +but memcg's group oom killing made it easier to trigger this bug by +calling wake_oom_reaper() on the same task from one out_of_memory() +request. + +Fix this bug using an approach used by commit 855b018325737f76 +("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). +Since task_will_free_mem(p) == false if p->mm == NULL, we can assume that +p->mm != NULL when wake_oom_reaper() is called from task_will_free_mem() +paths. As a side effect of this patch, this patch also avoids enqueuing +multiple threads sharing memory via task_will_free_mem(current) path. + +Signed-off-by: Tetsuo Handa +Reported-by: Arkadiusz Miśkiewicz +Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") +--- + mm/oom_kill.c | 28 +++++++++++++--------------- + 1 file changed, 13 insertions(+), 15 deletions(-) + +diff --git a/mm/oom_kill.c b/mm/oom_kill.c +index f0e8cd9..457f240 100644 +--- a/mm/oom_kill.c ++++ b/mm/oom_kill.c +@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm) + struct vm_area_struct *vma; + bool ret = true; + +- /* +- * Tell all users of get_user/copy_from_user etc... that the content +- * is no longer stable. No barriers really needed because unmapping +- * should imply barriers already and the reader would hit a page fault +- * if it stumbled over a reaped memory. +- */ +- set_bit(MMF_UNSTABLE, &mm->flags); +- + for (vma = mm->mmap ; vma; vma = vma->vm_next) { + if (!can_madv_dontneed_vma(vma)) + continue; +@@ -645,10 +637,15 @@ static int oom_reaper(void *unused) + return 0; + } + +-static void wake_oom_reaper(struct task_struct *tsk) ++static void wake_oom_reaper(struct task_struct *tsk, struct mm_struct *mm) + { +- /* tsk is already queued? */ +- if (tsk == oom_reaper_list || tsk->oom_reaper_list) ++ /* ++ * Tell all users of get_user/copy_from_user etc... that the content ++ * is no longer stable. No barriers really needed because unmapping ++ * should imply barriers already and the reader would hit a page fault ++ * if it stumbled over a reaped memory. ++ */ ++ if (test_and_set_bit(MMF_UNSTABLE, &mm->flags)) + return; + + get_task_struct(tsk); +@@ -668,7 +665,8 @@ static int __init oom_init(void) + } + subsys_initcall(oom_init) + #else +-static inline void wake_oom_reaper(struct task_struct *tsk) ++static inline void wake_oom_reaper(struct task_struct *tsk, ++ struct mm_struct *mm) + { + } + #endif /* CONFIG_MMU */ +@@ -915,7 +913,7 @@ static void __oom_kill_process(struct task_struct *victim) + rcu_read_unlock(); + + if (can_oom_reap) +- wake_oom_reaper(victim); ++ wake_oom_reaper(victim, mm); + + mmdrop(mm); + put_task_struct(victim); +@@ -955,7 +953,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message) + task_lock(p); + if (task_will_free_mem(p)) { + mark_oom_victim(p); +- wake_oom_reaper(p); ++ wake_oom_reaper(p, p->mm); + task_unlock(p); + put_task_struct(p); + return; +@@ -1085,7 +1083,7 @@ bool out_of_memory(struct oom_control *oc) + */ + if (task_will_free_mem(current)) { + mark_oom_victim(current); +- wake_oom_reaper(current); ++ wake_oom_reaper(current, current->mm); + return true; + } + +-- +1.8.3.1 + diff --git a/kernel.spec b/kernel.spec index 8f4a2257..551409d6 100644 --- a/kernel.spec +++ b/kernel.spec @@ -68,7 +68,7 @@ %define have_pcmcia 0 %endif -%define rel 1 +%define rel 2 %define basever 4.19 %define postver .16 -- 2.44.0