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linux-next/include
Davide Libenzi 3419b23a91 [PATCH] epoll: use unlocked wqueue operations
A few days ago Arjan signaled a lockdep red flag on epoll locks, and
precisely between the epoll's device structure lock (->lock) and the wait
queue head lock (->lock).

Like I explained in another email, and directly to Arjan, this can't happen
in reality because of the explicit check at eventpoll.c:592, that does not
allow to drop an epoll fd inside the same epoll fd.  Since lockdep is
working on per-structure locks, it will never be able to know of policies
enforced in other parts of the code.

It was decided time ago of having the ability to drop epoll fds inside
other epoll fds, that triggers a very trick wakeup operations (due to
possibly reentrant callback-driven wakeups) handled by the
ep_poll_safewake() function.  While looking again at the code though, I
noticed that all the operations done on the epoll's main structure wait
queue head (->wq) are already protected by the epoll lock (->lock), so that
locked-style functions can be used to manipulate the ->wq member.  This
makes both a lock-acquire save, and lockdep happy.

Running totalmess on my dual opteron for a while did not reveal any problem
so far:

http://www.xmailserver.org/totalmess.c

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-25 10:01:13 -07:00
..
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2006-06-23 07:52:36 -07:00
asm-alpha [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-arm [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-arm26 [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-cris Remove unneeded _syscallX macros from user view in asm-*/unistd.h 2006-04-29 01:51:47 +01:00
asm-frv [PATCH] frv: clean frv unistd.h 2006-06-23 07:42:55 -07:00
asm-generic [PATCH] introduce WARN_ON_ONCE(cond) 2006-06-25 10:01:11 -07:00
asm-h8300 [PATCH] adjust handle_IRR_event() return type 2006-06-23 07:43:08 -07:00
asm-i386 [PATCH] Make copy_from_user_inatomic NOT zero the tail on i386 2006-06-25 10:01:09 -07:00
asm-ia64 [PATCH] Define __raw_get_cpu_var and use it 2006-06-25 10:01:01 -07:00
asm-m32r [PATCH] vgacon: make VGA_MAP_MEM take size, remove extra use 2006-06-22 15:05:58 -07:00
asm-m68k [PATCH] m68k: convert VME irq code 2006-06-25 10:00:58 -07:00
asm-m68knommu [PATCH] adjust handle_IRR_event() return type 2006-06-23 07:43:08 -07:00
asm-mips [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-parisc [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-powerpc [PATCH] Define __raw_get_cpu_var and use it 2006-06-25 10:01:01 -07:00
asm-ppc [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-s390 [PATCH] Define __raw_get_cpu_var and use it 2006-06-25 10:01:01 -07:00
asm-sh [PATCH] random: remove SA_SAMPLE_RANDOM from floppy driver 2006-06-25 10:01:00 -07:00
asm-sh64 Remove unneeded _syscallX macros from user view in asm-*/unistd.h 2006-04-29 01:51:47 +01:00
asm-sparc [SBUS]: Rewrite and plug into of_device framework. 2006-06-23 23:15:50 -07:00
asm-sparc64 [PATCH] Define __raw_get_cpu_var and use it 2006-06-25 10:01:01 -07:00
asm-um Merge git://git.infradead.org/hdrcleanup-2.6 2006-06-20 15:10:08 -07:00
asm-v850 [PATCH] adjust handle_IRR_event() return type 2006-06-23 07:43:08 -07:00
asm-x86_64 [PATCH] Define __raw_get_cpu_var and use it 2006-06-25 10:01:01 -07:00
asm-xtensa [PATCH] xtensa: remove verify_area macros 2006-06-23 07:43:02 -07:00
keys
linux [PATCH] epoll: use unlocked wqueue operations 2006-06-25 10:01:13 -07:00
math-emu
media Revert include/media changes: Mauro says those ioctls are only used in-kernel(!) 2006-05-06 19:47:57 +01:00
mtd Merge git://git.infradead.org/hdrcleanup-2.6 2006-06-20 15:10:08 -07:00
net [NET]: fix net-core kernel-doc 2006-06-23 02:07:42 -07:00
pcmcia Don't include linux/config.h from anywhere else in include/ 2006-04-26 12:56:16 +01:00
rdma IB/uverbs: Don't serialize with ib_uverbs_idr_mutex 2006-06-17 20:44:49 -07:00
rxrpc
scsi Merge branch 'master' into upstream 2006-06-22 22:11:56 -04:00
sound [ALSA] version 1.0.12rc1 2006-06-22 21:35:11 +02:00
video Don't include linux/config.h from anywhere else in include/ 2006-04-26 12:56:16 +01:00