On Monday, September 26, 2011, Michal Hocko wrote: > On Mon 26-09-11 01:56:57, David Rientjes wrote: > > On Mon, 26 Sep 2011, Michal Hocko wrote: > > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > > index 626303b..b9774f3 100644 > > > --- a/mm/oom_kill.c > > > +++ b/mm/oom_kill.c > > > @@ -32,6 +32,7 @@ > > > #include <linux/mempolicy.h> > > > #include <linux/security.h> > > > #include <linux/ptrace.h> > > > +#include <linux/freezer.h> > > > > > > int sysctl_panic_on_oom; > > > int sysctl_oom_kill_allocating_task; > > > @@ -451,6 +452,9 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) > > > task_pid_nr(q), q->comm); > > > task_unlock(q); > > > force_sig(SIGKILL, q); > > > + > > > + if (frozen(q)) > > > + thaw_process(q); > > > } > > > > > > set_tsk_thread_flag(p, TIF_MEMDIE); > > > > This is in the wrong place, oom_kill_task() iterates over all threads that > > are _not_ in the same thread group as the chosen thread and kills them > > without giving them access to memory reserves. The chosen task, p, could > > still be frozen and may not exit. > > Ahh, right you are. I ave missed that one. Updated patch bellow. > > > > > Once that's fixed, feel free to add my > > > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > > Thanks > > > > > once Rafael sends his acked-by or reviewed-by. > --- > From f935ed4558c2fb033ef5c14e02b28e12a615f80e Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@xxxxxxx> > Date: Fri, 16 Sep 2011 11:23:15 +0200 > Subject: [PATCH] oom: do not live lock on frozen tasks > > Konstantin Khlebnikov has reported (https://lkml.org/lkml/2011/8/23/45) > that OOM can end up in a live lock if select_bad_process picks up a frozen > task. > Unfortunately we cannot mark such processes as unkillable to ignore them > because we could panic the system even though there is a chance that > somebody could thaw the process so we can make a forward process (e.g. a > process from another cpuset or with a different nodemask). > > Let's thaw an OOM selected frozen process right after we've sent fatal > signal from oom_kill_task. > Thawing is safe if the frozen task doesn't access any suspended device > (e.g. by ioctl) on the way out to the userspace where we handle the > signal and die. Note, we are not interested in the kernel threads because > they are not oom killable. > > Accessing suspended devices by a userspace processes shouldn't be an > issue because devices are suspended only after userspace is already > frozen and oom is disabled at that time. > > run_guest (drivers/lguest/core.c) calls try_to_freeze with an user > context but it seems it is able to cope with signals because it > explicitly checks for pending signals so we should be safe. > > Other than that userspace accesses the fridge only from the > signal handling routines so we are able to handle SIGKILL without any > negative side effects. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> > Reported-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> > --- > mm/oom_kill.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 626303b..c419a7e 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -32,6 +32,7 @@ > #include <linux/mempolicy.h> > #include <linux/security.h> > #include <linux/ptrace.h> > +#include <linux/freezer.h> > > int sysctl_panic_on_oom; > int sysctl_oom_kill_allocating_task; > @@ -451,10 +452,15 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem) > task_pid_nr(q), q->comm); > task_unlock(q); > force_sig(SIGKILL, q); > + > + if (frozen(q)) > + thaw_process(q); > } > > set_tsk_thread_flag(p, TIF_MEMDIE); > force_sig(SIGKILL, p); > + if (frozen(p)) > + thaw_process(p); > > return 0; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>