[tip:sched/urgent] cputime: Use local_clock() for full dynticks cputime accounting
From: tip-bot for Frederic Weisbecker
Date: Sun Feb 24 2013 - 07:24:30 EST
Commit-ID: 7f6575f1fb963d5231afbceecd3feadb6ab58cd3
Gitweb: http://git.kernel.org/tip/7f6575f1fb963d5231afbceecd3feadb6ab58cd3
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Sat, 23 Feb 2013 17:28:45 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 24 Feb 2013 12:57:16 +0100
cputime: Use local_clock() for full dynticks cputime accounting
Running the full dynticks cputime accounting with preemptible
kernel debugging trigger the following warning:
[ 4.488303] BUG: using smp_processor_id() in preemptible [00000000] code: init/1
[ 4.490971] caller is native_sched_clock+0x22/0x80
[ 4.493663] Pid: 1, comm: init Not tainted 3.8.0+ #13
[ 4.496376] Call Trace:
[ 4.498996] [<ffffffff813410eb>] debug_smp_processor_id+0xdb/0xf0
[ 4.501716] [<ffffffff8101e642>] native_sched_clock+0x22/0x80
[ 4.504434] [<ffffffff8101db99>] sched_clock+0x9/0x10
[ 4.507185] [<ffffffff81096ccd>] fetch_task_cputime+0xad/0x120
[ 4.509916] [<ffffffff81096dd5>] task_cputime+0x35/0x60
[ 4.512622] [<ffffffff810f146e>] acct_update_integrals+0x1e/0x40
[ 4.515372] [<ffffffff8117d2cf>] do_execve_common+0x4ff/0x5c0
[ 4.518117] [<ffffffff8117cf14>] ? do_execve_common+0x144/0x5c0
[ 4.520844] [<ffffffff81867a10>] ? rest_init+0x160/0x160
[ 4.523554] [<ffffffff8117d457>] do_execve+0x37/0x40
[ 4.526276] [<ffffffff810021a3>] run_init_process+0x23/0x30
[ 4.528953] [<ffffffff81867aac>] kernel_init+0x9c/0xf0
[ 4.531608] [<ffffffff8188356c>] ret_from_fork+0x7c/0xb0
We use sched_clock() to perform and fixup the cputime
accounting. However we are calling it with preemption enabled
from the read side, which trigger the bug above.
To fix this up, use local_clock() instead. It takes care of
preemption and also provide a more reliable clock source. This
is welcome for this kind of statistic that is widely relied on
in userspace.
Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reported-by: Ingo Molnar <mingo@xxxxxxxxxx>
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1361636925-22288-3-git-send-email-fweisbec@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/cputime.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 9857329..ed12cbb 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -604,7 +604,7 @@ static unsigned long long vtime_delta(struct task_struct *tsk)
{
unsigned long long clock;
- clock = sched_clock();
+ clock = local_clock();
if (clock < tsk->vtime_snap)
return 0;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/