The patch titled
taskstats_exit_alloc: optimize/simplify
has been added to the -mm tree. Its filename is
taskstats_exit_alloc-optimize-simplify.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: taskstats_exit_alloc: optimize/simplify
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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 <oleg@xxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/taskstats.c | 17 ++++-------------
1 files 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
@@ -421,7 +421,6 @@ 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
@@ -429,19 +428,11 @@ 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 */
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
xacct_add_tsk-fix-pure-theoretical-mm-use-after-free.patch
taskstats_exit_alloc-optimize-simplify.patch
tty-signal-tty-locking.patch
do_task_stat-dont-take-tty_mutex.patch
do_acct_process-dont-take-tty_mutex.patch
trivial-make-set_special_pids-static.patch
sys_unshare-remove-a-broken-clone_sighand-code.patch
sys_setpgid-eliminate-unnecessary-do_each_task_pidpidtype_pgid.patch
session_of_pgrp-kill-unnecessary-do_each_task_pidpidtype_pgid.patch
pidhash-temporary-debug-checks.patch
-
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