linux.git/fs/eventpoll.c, branch v2.6.25

lockdep: annotate epoll

2008-02-05T17:44:07+00:00

On Sat, 2008-01-05 at 13:35 -0800, Davide Libenzi wrote:

> I remember I talked with Arjan about this time ago. Basically, since 1)
> you can drop an epoll fd inside another epoll fd 2) callback-based wakeups
> are used, you can see a wake_up() from inside another wake_up(), but they
> will never refer to the same lock instance.
> Think about:
>
> 	dfd = socket(...);
> 	efd1 = epoll_create();
> 	efd2 = epoll_create();
> 	epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
> 	epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
>
> When a packet arrives to the device underneath "dfd", the net code will
> issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
> callback wakeup entry on that queue, and the wake_up() performed by the
> "dfd" net code will end up in ep_poll_callback(). At this point epoll
> (efd1) notices that it may have some event ready, so it needs to wake up
> the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
> that ends up in another wake_up(), after having checked about the
> recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
> avoid stack blasting. Never hit the same queue, to avoid loops like:
>
> 	epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
> 	epoll_ctl(efd3, EPOLL_CTL_ADD, efd2, ...);
> 	epoll_ctl(efd4, EPOLL_CTL_ADD, efd3, ...);
> 	epoll_ctl(efd1, EPOLL_CTL_ADD, efd4, ...);
>
> The code "if (tncur->wq == wq || ..." prevents re-entering the same
> queue/lock.

Since the epoll code is very careful to not nest same instance locks
allow the recursion.

Signed-off-by: Peter Zijlstra 
Tested-by: Stefan Richter 
Acked-by: Davide Libenzi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Use wake_up_locked() in eventpoll

2007-12-06T22:07:16+00:00

Replace the uses of __wake_up_locked with wake_up_locked

Signed-off-by: Matthew Wilcox

fs/eventpoll.c: use list_for_each_entry() instead of list_for_each()

2007-10-19T18:53:38+00:00

fs/eventpoll.c: use list_for_each_entry() instead of list_for_each()
in ep_poll_safewake()

Signed-off-by: Matthias Kaehlcke 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sparse pointer use of zero as null

2007-10-18T21:37:31+00:00

Get rid of sparse related warnings from places that use integer as NULL
pointer.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Stephen Hemminger 
Cc: Andi Kleen 
Cc: Jeff Garzik 
Cc: Matt Mackall 
Cc: Ian Kent 
Cc: Arnd Bergmann 
Cc: Davide Libenzi 
Cc: Stephen Smalley 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: Remove slab destructors from kmem_cache_create().

2007-07-20T01:11:58+00:00

Slab destructors were no longer supported after Christoph's
c59def9f222d44bb7e2f0a559f2906191a0862d7 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt

epoll: move kfree inside ep_free

2007-05-15T15:54:00+00:00

Move the kfree() call inside the ep_free() function.

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: fix some comments

2007-05-15T15:54:00+00:00

Fixes some epoll code comments.

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll locks changes and cleanups

2007-05-15T15:53:59+00:00

Changes the rwlock to a spinlock, and drops the use-count variable.
Operations are always bound by the mutex now, so the use-count is no more
needed.  For the same reason, the rwlock can become a simple spinlock.

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fix epoll single pass code and add wait-exclusive flag

2007-05-15T15:53:59+00:00

Fixes the epoll single pass code.  During the unlocked event delivery (to
userspace) code, the poll callback can re-issue new events, and we must
receive them correctly.  Since we loop in a lockless fashion, we want to be
O(nready), and we don't want to flash on/off the spinlock for every event, we
have the poll callback to use a secondary list to queue events while we're
inside the event delivery loop.  The rw_semaphore has been turned into a
mutex.  This patch also adds the wait-exclusive flag, as suggested by Davi
Arnaut.

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll cleanups: epoll remove static pre-declarations and akpm-ize the code

2007-05-11T15:29:37+00:00

Re-arrange epoll code to avoid static functions pre-declarations, and apply
akpm-filter on it.

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds