hus there is no need for a semaphore array list of pending operations. If - this list is removed - the per-semaphore array spinlock is removed (possible if there is no list to protect) - sem_otime is moved into the semaphores and calculated on demand during semctl() then the array would be read-mostly - which would significantly improve scaling for applications that use semaphore arrays with lots of entries. The price would be expensive semctl() calls: for(i=0;isem_nsems;i++) spin_lock(sma->sem_lock); for(i=0;isem_nsems;i++) spin_unlock(sma->sem_lock); I'm not sure if the complexity is worth the effort, thus here is the documentation of the current behavior first. 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 ;