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authorOleg Nesterov <oleg@tv-sign.ru>2006-06-26 03:26:08 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 12:58:27 -0400
commit7b1c6154fa8bb937e0b1b4f2adbb315d70270f10 (patch)
tree1d58e5e7da61330639ebe62671fb666596d1b00a /fs
parentd5f70c00ad24cd1158d3678b44ff969b4c971d49 (diff)
[PATCH] coredump: don't take tasklist_lock
This patch removes tasklist_lock from zap_threads(). This is safe wrt: do_exit: The caller holds mm->mmap_sem. This means that task which shares the same ->mm can't pass exit_mm(), so it can't be unhashed from init_task.tasks or ->thread_group lists. fork: None of sub-threads can fork after zap_process(leader). All processes which were created before this point should be visible to zap_threads() because copy_process() adds the new process to the tail of init_task.tasks list, and ->siglock lock/unlock provides a memory barrier. de_thread: It does list_replace_rcu(&leader->tasks, &current->tasks). So zap_threads() will see either old or new leader, it does not matter. However, it can change p->sighand, so we should use lock_task_sighand() in zap_process(). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/exec.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c
index b58ba7d127e0..49fa0127a330 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1373,7 +1373,11 @@ static void zap_process(struct task_struct *start)
1373 struct task_struct *t; 1373 struct task_struct *t;
1374 unsigned long flags; 1374 unsigned long flags;
1375 1375
1376 spin_lock_irqsave(&start->sighand->siglock, flags); 1376 /*
1377 * start->sighand can't disappear, but may be
1378 * changed by de_thread()
1379 */
1380 lock_task_sighand(start, &flags);
1377 start->signal->flags = SIGNAL_GROUP_EXIT; 1381 start->signal->flags = SIGNAL_GROUP_EXIT;
1378 start->signal->group_stop_count = 0; 1382 start->signal->group_stop_count = 0;
1379 1383
@@ -1386,7 +1390,7 @@ static void zap_process(struct task_struct *start)
1386 } 1390 }
1387 } while ((t = next_thread(t)) != start); 1391 } while ((t = next_thread(t)) != start);
1388 1392
1389 spin_unlock_irqrestore(&start->sighand->siglock, flags); 1393 unlock_task_sighand(start, &flags);
1390} 1394}
1391 1395
1392static void zap_threads(struct mm_struct *mm) 1396static void zap_threads(struct mm_struct *mm)
@@ -1404,7 +1408,7 @@ static void zap_threads(struct mm_struct *mm)
1404 complete(vfork_done); 1408 complete(vfork_done);
1405 } 1409 }
1406 1410
1407 read_lock(&tasklist_lock); 1411 rcu_read_lock();
1408 for_each_process(g) { 1412 for_each_process(g) {
1409 p = g; 1413 p = g;
1410 do { 1414 do {
@@ -1415,7 +1419,7 @@ static void zap_threads(struct mm_struct *mm)
1415 } 1419 }
1416 } while ((p = next_thread(p)) != g); 1420 } while ((p = next_thread(p)) != g);
1417 } 1421 }
1418 read_unlock(&tasklist_lock); 1422 rcu_read_unlock();
1419} 1423}
1420 1424
1421static void coredump_wait(struct mm_struct *mm) 1425static void coredump_wait(struct mm_struct *mm)