Btw. I do not think this patch should be in MM until we hear from Futex maintainers and also learn more about the underlying issue. Thanks. On Tue 07-12-21 15:49:24, Andrew Morton wrote: > From: Joel Savitz <jsavitz@xxxxxxxxxx> > Subject: mm/oom_kill: wake futex waiters before annihilating victim shared mutex > > In the case that two or more processes share a futex located within a > shared mmaped region, such as a process that shares a lock between itself > and a number of child processes, we have observed that when a process > holding the lock is oom killed, at least one waiter is never alerted to > this new development and simply continues to wait. > > This is visible via pthreads by checking the __owner field of the > pthread_mutex_t structure within a waiting process, perhaps with gdb. > > We identify reproduction of this issue by checking a waiting process of a > test program and viewing the contents of the pthread_mutex_t, taking note > of the value in the owner field, and then checking dmesg to see if the > owner has already been killed. > > This issue can be tricky to reproduce, but with the modifications of this > small patch, I have found it to be impossible to reproduce. There may be > additional considerations that I have not taken into account in this patch > and I welcome any comments and criticism. > > Link: https://lkml.kernel.org/r/20211207214902.772614-1-jsavitz@xxxxxxxxxx > Signed-off-by: Nico Pache <npache@xxxxxxxxxx> > Co-developed-by: Nico Pache <npache@xxxxxxxxxx> > Signed-off-by: Joel Savitz <jsavitz@xxxxxxxxxx> > Cc: Waiman Long <longman@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > mm/oom_kill.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- a/mm/oom_kill.c~mm-oom_kill-wake-futex-waiters-before-annihilating-victim-shared-mutex > +++ a/mm/oom_kill.c > @@ -44,6 +44,7 @@ > #include <linux/kthread.h> > #include <linux/init.h> > #include <linux/mmu_notifier.h> > +#include <linux/futex.h> > > #include <asm/tlb.h> > #include "internal.h" > @@ -890,6 +891,7 @@ static void __oom_kill_process(struct ta > * in order to prevent the OOM victim from depleting the memory > * reserves from the user space under its control. > */ > + futex_exit_release(victim); > do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID); > mark_oom_victim(victim); > pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n", > @@ -930,6 +932,7 @@ static void __oom_kill_process(struct ta > */ > if (unlikely(p->flags & PF_KTHREAD)) > continue; > + futex_exit_release(p); > do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID); > } > rcu_read_unlock(); > _ > > Patches currently in -mm which might be from jsavitz@xxxxxxxxxx are > > mm-oom_kill-wake-futex-waiters-before-annihilating-victim-shared-mutex.patch -- Michal Hocko SUSE Labs
