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[9/9] um: Properly check all process' threads for a live mm

Message ID 20120423070943.GI30752@lizard
State Accepted
Commit 2c922c51e6924298f8271d75732964f1ffdecaf2
Headers show

Commit Message

Anton Vorontsov April 23, 2012, 7:09 a.m. UTC
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 mbox

Patch

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);