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author | Eric Dumazet <edumazet@google.com> | 2015-08-28 19:42:30 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-09-05 13:46:58 -0700 |
commit | c82199061009d1561e31e17fca5e47a87cb7ff4c (patch) | |
tree | 547ec8ef61b4d70c57ff478d9d1de4853c373d92 /kernel/task_work.c | |
parent | f377ea88b862bf7151be96d276f4cb740f8e1c41 (diff) | |
download | op-kernel-dev-c82199061009d1561e31e17fca5e47a87cb7ff4c.zip op-kernel-dev-c82199061009d1561e31e17fca5e47a87cb7ff4c.tar.gz |
task_work: remove fifo ordering guarantee
In commit f341861fb0b ("task_work: add a scheduling point in
task_work_run()") I fixed a latency problem adding a cond_resched()
call.
Later, commit ac3d0da8f329 added yet another loop to reverse a list,
bringing back the latency spike :
I've seen in some cases this loop taking 275 ms, if for example a
process with 2,000,000 files is killed.
We could add yet another cond_resched() in the reverse loop, or we
can simply remove the reversal, as I do not think anything
would depend on order of task_work_add() submitted works.
Fixes: ac3d0da8f329 ("task_work: Make task_work_add() lockless")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Maciej Żenczykowski <maze@google.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/task_work.c')
-rw-r--r-- | kernel/task_work.c | 12 |
1 files changed, 2 insertions, 10 deletions
diff --git a/kernel/task_work.c b/kernel/task_work.c index 8727032..53fa971 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -18,6 +18,8 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ * This is like the signal handler which runs in kernel mode, but it doesn't * try to wake up the @task. * + * Note: there is no ordering guarantee on works queued here. + * * RETURNS: * 0 if succeeds or -ESRCH. */ @@ -108,16 +110,6 @@ void task_work_run(void) raw_spin_unlock_wait(&task->pi_lock); smp_mb(); - /* Reverse the list to run the works in fifo order */ - head = NULL; - do { - next = work->next; - work->next = head; - head = work; - work = next; - } while (work); - - work = head; do { next = work->next; work->func(work); |