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authorDavide Libenzi <davidel@xmailserver.org>2009-06-17 19:25:58 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-18 16:03:41 -0400
commit3fe4a975d662f11037cb710f8b4b158a3e38f9c0 (patch)
tree07986fcbf75f9a85c177aa3e7a2472e9833e4565 /fs/eventpoll.c
parent36025a812eebb34a478cfc1d3a538472591498b0 (diff)
epoll: fix nested calls support
This fixes a regression in 2.6.30. I unfortunately accepted a patch time ago, to drop the "current" usage from possible IRQ context, w/out proper thought over it. The patch switched to using the CPU id by bounding the nested call callback with a get_cpu()/put_cpu(). Unfortunately the ep_call_nested() function can be called with a callback that grabs sleepy locks (from own f_op->poll()), that results in epic fails. The following patch uses the proper "context" depending on the path where it is called, and on the kind of callback. This has been reported by Stefan Richter, that has also verified the patch is his previously failing environment. Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Reported-by: Stefan Richter <stefanr@s5r6.in-berlin.de> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/eventpoll.c')
-rw-r--r--fs/eventpoll.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 5458e80fc558..085c5c063420 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -98,7 +98,7 @@ struct epoll_filefd {
98struct nested_call_node { 98struct nested_call_node {
99 struct list_head llink; 99 struct list_head llink;
100 void *cookie; 100 void *cookie;
101 int cpu; 101 void *ctx;
102}; 102};
103 103
104/* 104/*
@@ -317,17 +317,17 @@ static void ep_nested_calls_init(struct nested_calls *ncalls)
317 * @nproc: Nested call core function pointer. 317 * @nproc: Nested call core function pointer.
318 * @priv: Opaque data to be passed to the @nproc callback. 318 * @priv: Opaque data to be passed to the @nproc callback.
319 * @cookie: Cookie to be used to identify this nested call. 319 * @cookie: Cookie to be used to identify this nested call.
320 * @ctx: This instance context.
320 * 321 *
321 * Returns: Returns the code returned by the @nproc callback, or -1 if 322 * Returns: Returns the code returned by the @nproc callback, or -1 if
322 * the maximum recursion limit has been exceeded. 323 * the maximum recursion limit has been exceeded.
323 */ 324 */
324static int ep_call_nested(struct nested_calls *ncalls, int max_nests, 325static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
325 int (*nproc)(void *, void *, int), void *priv, 326 int (*nproc)(void *, void *, int), void *priv,
326 void *cookie) 327 void *cookie, void *ctx)
327{ 328{
328 int error, call_nests = 0; 329 int error, call_nests = 0;
329 unsigned long flags; 330 unsigned long flags;
330 int this_cpu = get_cpu();
331 struct list_head *lsthead = &ncalls->tasks_call_list; 331 struct list_head *lsthead = &ncalls->tasks_call_list;
332 struct nested_call_node *tncur; 332 struct nested_call_node *tncur;
333 struct nested_call_node tnode; 333 struct nested_call_node tnode;
@@ -340,7 +340,7 @@ static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
340 * very much limited. 340 * very much limited.
341 */ 341 */
342 list_for_each_entry(tncur, lsthead, llink) { 342 list_for_each_entry(tncur, lsthead, llink) {
343 if (tncur->cpu == this_cpu && 343 if (tncur->ctx == ctx &&
344 (tncur->cookie == cookie || ++call_nests > max_nests)) { 344 (tncur->cookie == cookie || ++call_nests > max_nests)) {
345 /* 345 /*
346 * Ops ... loop detected or maximum nest level reached. 346 * Ops ... loop detected or maximum nest level reached.
@@ -352,7 +352,7 @@ static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
352 } 352 }
353 353
354 /* Add the current task and cookie to the list */ 354 /* Add the current task and cookie to the list */
355 tnode.cpu = this_cpu; 355 tnode.ctx = ctx;
356 tnode.cookie = cookie; 356 tnode.cookie = cookie;
357 list_add(&tnode.llink, lsthead); 357 list_add(&tnode.llink, lsthead);
358 358
@@ -364,10 +364,9 @@ static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
364 /* Remove the current task from the list */ 364 /* Remove the current task from the list */
365 spin_lock_irqsave(&ncalls->lock, flags); 365 spin_lock_irqsave(&ncalls->lock, flags);
366 list_del(&tnode.llink); 366 list_del(&tnode.llink);
367 out_unlock: 367out_unlock:
368 spin_unlock_irqrestore(&ncalls->lock, flags); 368 spin_unlock_irqrestore(&ncalls->lock, flags);
369 369
370 put_cpu();
371 return error; 370 return error;
372} 371}
373 372
@@ -408,8 +407,12 @@ static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
408 */ 407 */
409static void ep_poll_safewake(wait_queue_head_t *wq) 408static void ep_poll_safewake(wait_queue_head_t *wq)
410{ 409{
410 int this_cpu = get_cpu();
411
411 ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, 412 ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
412 ep_poll_wakeup_proc, NULL, wq); 413 ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
414
415 put_cpu();
413} 416}
414 417
415/* 418/*
@@ -663,7 +666,7 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
663 * could re-enter here. 666 * could re-enter here.
664 */ 667 */
665 pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, 668 pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
666 ep_poll_readyevents_proc, ep, ep); 669 ep_poll_readyevents_proc, ep, ep, current);
667 670
668 return pollflags != -1 ? pollflags : 0; 671 return pollflags != -1 ? pollflags : 0;
669} 672}