linux.git/fs/eventpoll.c, branch v2.6.32

epoll: fix nested calls support

2009-06-18T20:03:41+00:00

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 
Reported-by: Stefan Richter 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: fix size check in epoll_create()

2009-05-12T21:11:35+00:00

Fix a size check WRT the manual pages.  This was inadvertently broken by
commit 9fe5ad9c8cef9ad5873d8ee55d1cf00d9b607df0 ("flag parameters
add-on: remove epoll_create size param").

Signed-off-by: Davide Libenzi 
Cc: 
Cc: rohit verma 
Cc: Ulrich Drepper 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll keyed wakeups: teach epoll about hints coming with the wakeup key

2009-04-01T15:59:20+00:00

Use the events hint now sent by some devices, to avoid unnecessary wakeups
for events that are of no interest for the caller.  This code handles both
devices that are sending keyed events, and the ones that are not (and
event the ones that sometimes send events, and sometimes don't).

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Davide Libenzi 
Cc: Alan Cox 
Cc: Ingo Molnar 
Cc: David Miller 
Cc: William Lee Irwin III 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: use real type instead of void *

2009-04-01T15:59:20+00:00

eventpoll.c uses void * in one place for no obvious reason; change it to
use the real type instead.

Signed-off-by: Tony Battersby 
Acked-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: clean up ep_modify

2009-04-01T15:59:19+00:00

ep_modify() doesn't need to set event.data from within the ep->lock
spinlock as the comment suggests.  The only place event.data is used is
ep_send_events_proc(), and this is protected by ep->mtx instead of
ep->lock.  Also update the comment for mutex_lock() at the top of
ep_scan_ready_list(), which mentions epoll_ctl(EPOLL_CTL_DEL) but not
epoll_ctl(EPOLL_CTL_MOD).

ep_modify() can also use spin_lock_irq() instead of spin_lock_irqsave().

Signed-off-by: Tony Battersby 
Acked-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: remove unnecessary xchg

2009-04-01T15:59:19+00:00

xchg in ep_unregister_pollwait() is unnecessary because it is protected by
either epmutex or ep->mtx (the same protection as ep_remove()).

If xchg was necessary, it would be insufficient to protect against
problems: if multiple concurrent calls to ep_unregister_pollwait() were
possible then a second caller that returns without doing anything because
nwait == 0 could return before the waitqueues are removed by the first
caller, which looks like it could lead to problematic races with
ep_poll_callback().

So remove xchg and add comments about the locking.

Signed-off-by: Tony Battersby 
Acked-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: remember the event if epoll_wait returns -EFAULT

2009-04-01T15:59:19+00:00

If epoll_wait returns -EFAULT, the event that was being returned when the
fault was encountered will be forgotten.  This is not a big deal since
EFAULT will happen only if a buggy userspace program passes in a bad
address, in which case what happens later usually doesn't matter.
However, it is easy to remember the event for later, and this patch makes
a simple change to do that.

Signed-off-by: Tony Battersby 
Acked-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: don't use current in irq context

2009-04-01T15:59:19+00:00

ep_call_nested() (formerly ep_poll_safewake()) uses "current" (without
dereferencing it) to detect callback recursion, but it may be called from
irq context where the use of current is generally discouraged.  It would
be better to use get_cpu() and put_cpu() to detect the callback recursion.

Signed-off-by: Tony Battersby 
Acked-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: remove debugging code

2009-04-01T15:59:19+00:00

Remove debugging code from epoll.  There's no need for it to be included
into mainline code.

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

epoll: fix epoll's own poll (update)

2009-04-01T15:59:19+00:00

Signed-off-by: Davide Libenzi 
Cc: Pavel Pisa 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds