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um: properly check all process' threads for a live mm 

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>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Anton Vorontsov 2012-05-31 16:26:26 -07:00 committed by Linus Torvalds
parent 137d1a26c8
commit 2c922c51e6
1 changed files with 7 additions and 6 deletions
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13
arch/um/kernel/reboot.c
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@ -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);