On Thu, 25 Mar 2010 00:25:05 +0800
Anfei Zhou <anfei.zhou@xxxxxxxxx> wrote:
> In multi-threading environment, if the current task(A) have got
> the mm->mmap_sem semaphore, and the thread(B) in the same process
> is selected to be oom killed, because they shares the same semaphore,
> thread B can not really be killed. So __alloc_pages_slowpath turns
> to be a infinite loop. Here set all the threads in the group to
> TIF_MEMDIE, it gets a chance to break and exit.
>
> Signed-off-by: Anfei Zhou <anfei.zhou@xxxxxxxxx>
> ---
> mm/oom_kill.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 9b223af..aab9892 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -381,6 +381,8 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
> */
> static void __oom_kill_task(struct task_struct *p, int verbose)
> {
> + struct task_struct *t;
> +
> if (is_global_init(p)) {
> WARN_ON(1);
> printk(KERN_WARNING "tried to kill init!\n");
> @@ -412,6 +414,8 @@ static void __oom_kill_task(struct task_struct *p, int verbose)
> */
> p->rt.time_slice = HZ;
> set_tsk_thread_flag(p, TIF_MEMDIE);
> + for (t = next_thread(p); t != p; t = next_thread(t))
> + set_tsk_thread_flag(t, TIF_MEMDIE);
>
> force_sig(SIGKILL, p);
Don't we need some sort of locking while walking that ring?
Unintuitively it appears to be spin_lock_irq(&p->sighand->siglock).
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