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Wed, 10 Sep 2025 08:24:08 -0700 (PDT) MIME-Version: 1.0 References: <20250910143726.19905-1-zhongjinji@honor.com> <20250910143726.19905-2-zhongjinji@honor.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 10 Sep 2025 08:23:56 -0700 X-Gm-Features: AS18NWAJ45hQ9B-n7p6XQn7GBwUVm3h_aYmSoIZyWzjk4e_caUPvzXaPHJVMs7E Message-ID: Subject: Re: [PATCH v9 1/2] mm/oom_kill: Thaw the entire OOM victim process To: Michal Hocko Cc: zhongjinji , rientjes@google.com, shakeel.butt@linux.dev, akpm@linux-foundation.org, tglx@linutronix.de, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, lenb@kernel.org, rafael@kernel.org, pavel@kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, liulu.liu@honor.com, feng.han@honor.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: A7BC340015 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 8g7igmffdz4fgtn5o779gmc168wst3fp X-HE-Tag: 1757517850-289805 X-HE-Meta: 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 8lFnlPjH yt/tTE+thuoGrbShT1Md/IOHhKXXMchwAKQXpdzhbZho2hlatlCpbEsbqTlNQW4eS7iNqtt464+RQfZA7l+qC3yQ/yHGdOV0TScmdROIMaCPaT8I40fxrU0H2+S1hgAALRHRq2d7LMjhoSVaGaYes+ax1/saU+naLbMVZu6aYLp1uL7DK5nGkAaG4rRqgMyDV5ULSrroBCNF9fQNj67vCbuq2vlVNEXVZwflX7fP97yvQrK1WZEXlel+bmTrUtiOdotdvVTHBXRKC38/Ysp7pJfelyzltVQ9p5q+YrbZVLKA0NxWzG6eeZGsGNjPIQuLe0gUo0iUrpvpijuK2zSAIySRgucC1nD8e8Y/KejpFG5C9VrafclKO8xKk0YjCV1fPi2oRuacul244yhhBVsSvuedxeKKqSl6N1hNLLfYV7fHs3mo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 10, 2025 at 8:15=E2=80=AFAM Michal Hocko wrot= e: > > On Wed 10-09-25 22:37:25, zhongjinji wrote: > > OOM killer is a mechanism that selects and kills processes when the sys= tem > > runs out of memory to reclaim resources and keep the system stable. But= the > > oom victim cannot terminate on its own when it is frozen, even if the O= OM > > victim task is thawed through __thaw_task(). This is because __thaw_tas= k() can > > only thaw a single OOM victim thread, and cannot thaw the entire OOM vi= ctim > > process. > > > > Also, freezing_slow_path() decides whether a task is an OOM victim by c= hecking > > the task's TIF_MEMDIE flag. When a task is thawed, the freezer bypasses= PM > > freezing and cgroup freezing states to thaw it. But TIF_MEMDIE is not a= thread > > group shared flag, and only one thread is marked with TIF_MEMDIE. If ot= her > > threads are thawed, they may still remain frozen due to PM freezing and= cgroup > > freezing states. > > > > To solve this, thaw_process() is introduced to thaw all threads of the = victim, > > ensuring every thread in the victim process can be thawed. The freezer = uses > > tsk_is_oom_victim() to determine whether a task is an OOM victim, becau= se > > tsk->signal->oom_mm is data shared by all threads. This allows all vict= im threads > > to rely on it to be thawed. > > A history detour for future reference. > TIF_MEMDIE was a "this is the oom victim & it has access to memory > reserves" flag in the past. It has that thread vs. process problems and > tsk_is_oom_victim was introduced later to get rid of them and other > issues as well as the guarantee that we can identify the oom victim's mm = reliably > for other oom_reaper. I recommend reading git log of mm/oom_kill.c to > get hairy history of that area and how tricky it is due all the subtle > interaction with process exit paths etc. > > > > > This change will thaw the entire victim process when OOM occurs, > > ensuring that the oom victim can terminate on its own. > > > > Signed-off-by: zhongjinji > > Acked-by: Michal Hocko > Thanks! Reviewed-by: Suren Baghdasaryan > > > > Acked-by: Michal Hocko > > --- > > include/linux/freezer.h | 2 ++ > > kernel/freezer.c | 20 +++++++++++++++++++- > > mm/oom_kill.c | 10 +++++----- > > 3 files changed, 26 insertions(+), 6 deletions(-) > > > > diff --git a/include/linux/freezer.h b/include/linux/freezer.h > > index b303472255be..32884c9721e5 100644 > > --- a/include/linux/freezer.h > > +++ b/include/linux/freezer.h > > @@ -47,6 +47,7 @@ extern int freeze_processes(void); > > extern int freeze_kernel_threads(void); > > extern void thaw_processes(void); > > extern void thaw_kernel_threads(void); > > +extern void thaw_process(struct task_struct *p); > > > > static inline bool try_to_freeze(void) > > { > > @@ -80,6 +81,7 @@ static inline int freeze_processes(void) { return -EN= OSYS; } > > static inline int freeze_kernel_threads(void) { return -ENOSYS; } > > static inline void thaw_processes(void) {} > > static inline void thaw_kernel_threads(void) {} > > +static inline void thaw_process(struct task_struct *p) {} > > > > static inline bool try_to_freeze(void) { return false; } > > > > diff --git a/kernel/freezer.c b/kernel/freezer.c > > index 6a96149aede9..ddc11a8bd2ea 100644 > > --- a/kernel/freezer.c > > +++ b/kernel/freezer.c > > @@ -10,6 +10,7 @@ > > #include > > #include > > #include > > +#include > > #include > > > > /* total number of freezing conditions in effect */ > > @@ -40,7 +41,7 @@ bool freezing_slow_path(struct task_struct *p) > > if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK)) > > return false; > > > > - if (test_tsk_thread_flag(p, TIF_MEMDIE)) > > + if (tsk_is_oom_victim(p)) > > return false; > > > > if (pm_nosig_freezing || cgroup_freezing(p)) > > @@ -206,6 +207,23 @@ void __thaw_task(struct task_struct *p) > > wake_up_state(p, TASK_FROZEN); > > } > > > > +/* > > + * thaw_process - Thaw a frozen process > > + * @p: the process to be thawed > > + * > > + * Iterate over all threads of @p and call __thaw_task() on each. > > + */ > > +void thaw_process(struct task_struct *p) > > +{ > > + struct task_struct *t; > > + > > + rcu_read_lock(); > > + for_each_thread(p, t) { > > + __thaw_task(t); > > + } > > + rcu_read_unlock(); > > +} > > + > > /** > > * set_freezable - make %current freezable > > * > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 25923cfec9c6..88356b66cc35 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -772,12 +772,12 @@ static void mark_oom_victim(struct task_struct *t= sk) > > mmgrab(tsk->signal->oom_mm); > > > > /* > > - * Make sure that the task is woken up from uninterruptible sleep > > - * if it is frozen because OOM killer wouldn't be able to free > > - * any memory and livelock. freezing_slow_path will tell the free= zer > > - * that TIF_MEMDIE tasks should be ignored. > > + * Make sure that the process is woken up from uninterruptible sl= eep > > + * if it is frozen because OOM killer wouldn't be able to free an= y > > + * memory and livelock. The freezer will thaw the tasks that are = OOM > > + * victims regardless of the PM freezing and cgroup freezing stat= es. > > */ > > - __thaw_task(tsk); > > + thaw_process(tsk); > > atomic_inc(&oom_victims); > > cred =3D get_task_cred(tsk); > > trace_mark_victim(tsk, cred->uid.val); > > -- > > 2.17.1 > > -- > Michal Hocko > SUSE Labs >