kill_off_processes() might miss a valid process, this is because checking for process->mm is not enough. Process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm.
To catch this we use find_lock_task_mm(), which walks up all threads and returns an appropriate task (with task lock held).
Suggested-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- arch/um/kernel/reboot.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c index 1411f4e..3d15243 100644 --- a/arch/um/kernel/reboot.c +++ b/arch/um/kernel/reboot.c @@ -6,6 +6,7 @@ #include "linux/sched.h" #include "linux/spinlock.h" #include "linux/slab.h" +#include "linux/oom.h" #include "kern_util.h" #include "os.h" #include "skas.h" @@ -25,13 +26,13 @@ static void kill_off_processes(void)
read_lock(&tasklist_lock); for_each_process(p) { - task_lock(p); - if (!p->mm) { - task_unlock(p); + struct task_struct *t; + + t = find_lock_task_mm(p); + if (!t) continue; - } - pid = p->mm->context.id.u.pid; - task_unlock(p); + pid = t->mm->context.id.u.pid; + task_unlock(t); os_kill_ptraced_process(pid, 1); } read_unlock(&tasklist_lock);