From: Oleg Nesterov If there are no listeners, every task does unneeded kmem_cache alloc/free on exit. We don't need listeners->sem for 'if (!list_empty())' check. Yes, we may have a false positive, but this doesn't differ from the case when the listener is unregistered after we drop the semaphore. So we don't need to do allocation beforehand. Signed-off-by: Oleg Nesterov Cc: Balbir Singh Acked-by: Shailabh Nagar Signed-off-by: Andrew Morton --- kernel/taskstats.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff -puN kernel/taskstats.c~taskstats_exit_alloc-optimize-simplify kernel/taskstats.c --- a/kernel/taskstats.c~taskstats_exit_alloc-optimize-simplify +++ a/kernel/taskstats.c @@ -416,7 +416,6 @@ err: void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu) { struct listener_list *listeners; - struct taskstats *tmp; /* * This is the cpu on which the task is exiting currently and will * be the one for which the exit event is sent, even if the cpu @@ -424,19 +423,11 @@ void taskstats_exit_alloc(struct tasksta */ *mycpu = raw_smp_processor_id(); - *ptidstats = NULL; - tmp = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL); - if (!tmp) - return; - listeners = &per_cpu(listener_array, *mycpu); - down_read(&listeners->sem); - if (!list_empty(&listeners->list)) { - *ptidstats = tmp; - tmp = NULL; - } - up_read(&listeners->sem); - kfree(tmp); + + *ptidstats = NULL; + if (!list_empty(&listeners->list)) + *ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL); } /* Send pid data out on exit */ _