linux-toradex.git/include/linux/sem.h, branch v4.6-rc6

ipc/sem.c: replace shared sem_otime with per-semaphore value

2013-07-09T17:33:28+00:00

sem_otime contains the time of the last semaphore operation that
completed successfully.  Every operation updates this value, thus access
from multiple cpus can cause thrashing.

Therefore the patch replaces the variable with a per-semaphore variable.
The per-array sem_otime is only calculated when required.

No performance improvement on a single-socket i3 - only important for
larger systems.

Signed-off-by: Manfred Spraul 
Cc: Rik van Riel 
Cc: Davidlohr Bueso 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem: separate wait-for-zero and alter tasks into seperate queues

2013-07-09T17:33:28+00:00

Introduce separate queues for operations that do not modify the
semaphore values.  Advantages:

 - Simpler logic in check_restart().
 - Faster update_queue(): Right now, all wait-for-zero operations are
   always tested, even if the semaphore value is not 0.
 - wait-for-zero gets again priority, as in linux <=3.0.9

Signed-off-by: Manfred Spraul 
Cc: Rik van Riel 
Cc: Davidlohr Bueso 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48+00:00

Signed-off-by: David Howells 
Acked-by: Arnd Bergmann 
Acked-by: Thomas Gleixner 
Acked-by: Michael Kerrisk 
Acked-by: Paul E. McKenney 
Acked-by: Dave Jones

include/linux/sem.h: make sysv_sem empty if SYSVIPC is disabled

2011-11-02T23:07:01+00:00

For the sysvsem undo, each task struct contains a sysv_sem structure with
a pointer to the undo information.

This pointer is only necessary if sysvipc is enabled - thus the pointer
can be made conditional on CONFIG_SYSVIPC.

Signed-off-by: Manfred Spraul 
Acked-by: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Mike Galbraith 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem.c: remove private structures from public header file

2011-11-02T23:07:01+00:00

include/linux/sem.h contains several structures that are only used within
ipc/sem.c.

The patch moves them into ipc/sem.c - there is no need to expose the
structures to the whole kernel.

No functional changes, only whitespace cleanups and 80-char per line
fixes.

Signed-off-by: Manfred Spraul 
Acked-by: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Mike Galbraith 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

atomic: use

2011-07-26T23:49:47+00:00

This allows us to move duplicated code in 
(atomic_inc_not_zero() for now) to 

Signed-off-by: Arun Sharma 
Reviewed-by: Eric Dumazet 
Cc: Ingo Molnar 
Cc: David Miller 
Cc: Eric Dumazet 
Acked-by: Mike Frysinger 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem.c: cacheline align the ipc spinlock for semaphores

2010-05-27T16:12:49+00:00

Cacheline align the spinlock for sysv semaphores.  Without the patch, the
spinlock and sem_otime [written by every semop that modified the array]
and sem_base [read in the hot path of try_atomic_semop()] can be in the
same cacheline.

Signed-off-by: Manfred Spraul 
Cc: Chris Mason 
Cc: Zach Brown 
Cc: Jens Axboe 
Cc: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem.c: add a per-semaphore pending list

2009-12-16T15:20:10+00:00

Based on Nick's findings:

sysv sem has the concept of semaphore arrays that consist out of multiple
semaphores.  Atomic operations that affect multiple semaphores are
supported.

The patch is the first step for optimizing simple, single semaphore
operations: In addition to the global list of all pending operations, a
2nd, per-semaphore list with the simple operations is added.

Note: this patch does not make sense by itself, the new list is used
nowhere.

Signed-off-by: Manfred Spraul 
Cc: Nick Piggin 
Cc: Pierre Peiffer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem.c: rewrite undo list locking

2008-07-25T17:53:42+00:00

The attached patch:
- reverses the locking order of ulp->lock and sem_lock:
  Previously, it was first ulp->lock, then inside sem_lock.
  Now it's the other way around.
- converts the undo structure to rcu.

Benefits:
- With the old locking order, IPC_RMID could not kfree the undo structures.
  The stale entries remained in the linked lists and were released later.
- The patch fixes a a race in semtimedop(): if both IPC_RMID and a semget() that
  recreates exactly the same id happen between find_alloc_undo() and sem_lock,
  then semtimedop() would access already kfree'd memory.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul 
Reviewed-by: Nadia Derbey 
Cc: Pierre Peiffer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/sem.c: convert sem_array.sem_pending to struct list_head

2008-07-25T17:53:42+00:00

sem_array.sem_pending is a double linked list, the attached patch converts
it to struct list_head.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul 
Reviewed-by: Nadia Derbey 
Cc: Pierre Peiffer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds