user/sven/linux.git/ipc/sem.c, branch v3.15.6

ipc: remove braces for single statements

2014-01-28T05:02:39Z

Deal with checkpatch messages: WARNING: braces {} are not necessary for single statement blocks Signed-off-by: Davidlohr Bueso Cc: Aswin Chandramouleeswaran Cc: Rik van Riel Acked-by: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: standardize code comments

2014-01-28T05:02:39Z

IPC commenting style is all over the place, *specially* in util.c. This patch orders things a bit. Signed-off-by: Davidlohr Bueso Cc: Aswin Chandramouleeswaran Cc: Rik van Riel Acked-by: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: whitespace cleanup

2014-01-28T05:02:39Z

The ipc code does not adhere the typical linux coding style. This patch fixes lots of simple whitespace errors. - mostly autogenerated by scripts/checkpatch.pl -f --fix \ --types=pointer_location,spacing,space_before_tab - one manual fixup (keep structure members tab-aligned) - removal of additional space_before_tab that were not found by --fix Tested with some of my msg and sem test apps. Andrew: Could you include it in -mm and move it towards Linus' tree? Signed-off-by: Manfred Spraul Suggested-by: Li Bin Cc: Joe Perches Acked-by: Rafael Aquini Cc: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: change kern_ipc_perm.deleted type to bool

2014-01-28T05:02:39Z

struct kern_ipc_perm.deleted is meant to be used as a boolean toggle, and the changes introduced by this patch are just to make the case explicit. Signed-off-by: Rafael Aquini Reviewed-by: Rik van Riel Cc: Greg Thelen Acked-by: Davidlohr Bueso Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: introduce ipc_valid_object() helper to sort out IPC_RMID races

2014-01-28T05:02:39Z

After the locking semantics for the SysV IPC API got improved, a couple of IPC_RMID race windows were opened because we ended up dropping the 'kern_ipc_perm.deleted' check performed way down in ipc_lock(). The spotted races got sorted out by re-introducing the old test within the racy critical sections. This patch introduces ipc_valid_object() to consolidate the way we cope with IPC_RMID races by using the same abstraction across the API implementation. Signed-off-by: Rafael Aquini Acked-by: Rik van Riel Acked-by: Greg Thelen Reviewed-by: Davidlohr Bueso Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc/sem.c: avoid overflow of semop undo (semadj) value

2014-01-28T05:02:39Z

When trying to understand semop code, I found a small mistake in the check for semadj (undo) value overflow. The new undo value is not stored immediately and next potential checks are done against the old value. The failing scenario is not much practical. One semop call has to do more operations on the same semaphore. Also semval and semadj must have different values, so there has to be some operations without SEM_UNDO flag. For example: struct sembuf depositor_op[1]; struct sembuf collector_op[2]; depositor_op[0].sem_num = 0; depositor_op[0].sem_op = 20000; depositor_op[0].sem_flg = 0; collector_op[0].sem_num = 0; collector_op[0].sem_op = -10000; collector_op[0].sem_flg = SEM_UNDO; collector_op[1].sem_num = 0; collector_op[1].sem_op = -10000; collector_op[1].sem_flg = SEM_UNDO; if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 1st deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 1st collect"); return 1; } if (semop(semid, depositor_op, 1) == -1) { perror("Failed to do 2nd deposit"); return 1; } if (semop(semid, collector_op, 2) == -1) { perror("Failed to do 2nd collect"); return 1; } return 0; It passes without error now but the semadj value has overflown in the 2nd collector operation. [akpm@linux-foundation.org: restore lessened scope of local `undo'] [davidlohr@hp.com: correct header comment for perform_atomic_semop] Signed-off-by: Petr Mladek Acked-by: Davidlohr Bueso Acked-by: Manfred Spraul Cc: Jiri Kosina Signed-off-by: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc/sem.c: synchronize semop and semctl with IPC_RMID

2013-10-17T04:35:52Z

After acquiring the semlock spinlock, operations must test that the array is still valid. - semctl() and exit_sem() would walk stale linked lists (ugly, but should be ok: all lists are empty) - semtimedop() would sleep forever - and if woken up due to a signal - access memory after free. The patch also: - standardizes the tests for .deleted, so that all tests in one function leave the function with the same approach. - unconditionally tests for .deleted immediately after every call to sem_lock - even it it means that for semctl(GETALL), .deleted will be tested twice. Both changes make the review simpler: After every sem_lock, there must be a test of .deleted, followed by a goto to the cleanup code (if the function uses "goto cleanup"). The only exception is semctl_down(): If sem_ids().rwsem is locked, then the presence in ids->ipcs_idr is equivalent to !.deleted, thus no additional test is required. Signed-off-by: Manfred Spraul Cc: Mike Galbraith Acked-by: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc/sem.c: update sem_otime for all operations

2013-09-30T21:31:03Z

In commit 0a2b9d4c7967 ("ipc/sem.c: move wake_up_process out of the spinlock section"), the update of semaphore's sem_otime(last semop time) was moved to one central position (do_smart_update). But since do_smart_update() is only called for operations that modify the array, this means that wait-for-zero semops do not update sem_otime anymore. The fix is simple: Non-alter operations must update sem_otime. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Manfred Spraul Reported-by: Jia He Tested-by: Jia He Cc: Davidlohr Bueso Cc: Mike Galbraith Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc/sem.c: synchronize the proc interface

2013-09-30T21:31:01Z

The proc interface is not aware of sem_lock(), it instead calls ipc_lock_object() directly. This means that simple semop() operations can run in parallel with the proc interface. Right now, this is uncritical, because the implementation doesn't do anything that requires a proper synchronization. But it is dangerous and therefore should be fixed. Signed-off-by: Manfred Spraul Cc: Davidlohr Bueso Cc: Mike Galbraith Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc/sem.c: optimize sem_lock()

2013-09-30T21:31:01Z

Operations that need access to the whole array must guarantee that there are no simple operations ongoing. Right now this is achieved by spin_unlock_wait(sem->lock) on all semaphores. If complex_count is nonzero, then this spin_unlock_wait() is not necessary, because it was already performed in the past by the thread that increased complex_count and even though sem_perm.lock was dropped inbetween, no simple operation could have started, because simple operations cannot start when complex_count is non-zero. Signed-off-by: Manfred Spraul Cc: Mike Galbraith Cc: Rik van Riel Reviewed-by: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds