linux/ipc
Nick Piggin d4212093dc ipc/sem.c: sem preempt improve
The strange sysv semaphore wakeup scheme has a kind of busy-wait lock
involved, which could deadlock if preemption is enabled during the "lock".

It is an implementation detail (due to a spinlock being held) that this is
actually the case.  However if "spinlocks" are made preemptible, or if the
sem lock is changed to a sleeping lock for example, then the wakeup would
become buggy.  So this might be a bugfix for -rt kernels.

Imagine waker being preempted by wakee and never clearing IN_WAKEUP -- if
wakee has higher RT priority then there is a priority inversion deadlock.
Even if there is not a priority inversion to cause a deadlock, then there
is still time wasted spinning.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-12-16 07:20:09 -08:00
..
compat_mq.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
compat.c fix logic error in ipc compat semctl() 2007-07-06 10:23:43 -07:00
ipc_sysctl.c sysctl ipc: Remove dead binary sysctl support code. 2009-11-12 02:04:54 -08:00
ipcns_notifier.c ipc: do not use a negative value to re-enable msgmni automatic recomputing 2008-07-25 10:53:42 -07:00
Makefile namespaces: mqueue namespace: adapt sysctl 2009-04-07 08:31:09 -07:00
mq_sysctl.c sysctl ipc: Remove dead binary sysctl support code. 2009-11-12 02:04:54 -08:00
mqueue.c const: mark remaining super_operations const 2009-09-22 07:17:24 -07:00
msg.c ipc ns: fix memory leak (idr) 2009-12-16 07:20:09 -08:00
msgutil.c namespaces: ipc namespaces: implement support for posix msqueues 2009-04-07 08:31:09 -07:00
namespace.c ipcns: make free_ipc_ns() static 2009-06-18 13:03:56 -07:00
sem.c ipc/sem.c: sem preempt improve 2009-12-16 07:20:09 -08:00
shm.c ipc ns: fix memory leak (idr) 2009-12-16 07:20:09 -08:00
util.c seq_file: constify seq_operations 2009-09-23 07:39:29 -07:00
util.h ipc: unbreak 32-bit shmctl/semctl/msgctl 2009-06-21 12:48:43 -07:00