On 04/16/2013 04:06 AM, Stanislaw Gruszka wrote: > On Thu, Apr 11, 2013 at 11:47:37AM -0700, Dave Hansen wrote: >> On 04/11/2013 12:45 AM, Stanislaw Gruszka wrote: >>> On Mon, Apr 08, 2013 at 08:57:16AM -0700, Dave Hansen wrote: >>>> On 04/04/2013 04:41 PM, Frederic Weisbecker wrote: >>>>> Does this patch fix the issue for you? >>>>> https://lkml.org/lkml/2013/4/4/112 >>>> >>>> Nope, that doesn't seem to make a difference. I'm still seeing the >>>> underflow. I'm pretty sure it's already gone to hell by the time it >>>> gets in to the loop that's patched there. >>> >>> Perhaps this is glich introduced by commit >>> 62188451f0d63add7ad0cd2a1ae269d600c1663d "cputime: Avoid multiplication >>> overflow on utime scaling" . Could you try to revert it and see if that >>> helps. If it does not, can you check if problem happen on 3.8 ? >> >> I'll run a bit longer, but reverting >> 62188451f0d63add7ad0cd2a1ae269d600c1663d _does_ seem to make it happier. > > Hmm, I supposed glitch in this commit because it something that was > changed recently and previously we did not have such bug reports. But > I do not see mistake there. Basically prev->stime should never be > bigger than rtime, since at any moment stime <= rtime and previous > rtime <= current rtime. So this looks like rtime decrease and for > some reason before 62188451f0d it does not manifest as a bug. > > It can be fixed by comparing prev->stime < rtime or by something > like first attached patch. Not sure what will be better.
The first patch does appear to fix the issue for me. > But since this (most likely) is rtime monotonicity problem it > is bug by itself and probably that should be fixed. Can you > check second patch attached and see if it trigger the warning. Yup, it triggers lots of warnings. Here's one. > [ 460.789710] ------------[ cut here ]------------ > [ 460.789730] WARNING: at > /home/davehans/linux.git/kernel/sched/cputime.c:563 cputime_adjust+0xe6/0xf0() > [ 460.789736] Hardware name: PRIMEQUEST 1800E2 > [ 460.789739] Modules linked in: > [ 460.789745] Pid: 4245, comm: top Tainted: G W > 3.9.0-rc7-00004-gbb33db7-dirty #19 > [ 460.789748] Call Trace: > [ 460.789777] [<ffffffff810c6dc7>] warn_slowpath_common+0xb7/0x120 > [ 460.789783] [<ffffffff810c6e5a>] warn_slowpath_null+0x2a/0x40 > [ 460.789789] [<ffffffff8111a8d6>] cputime_adjust+0xe6/0xf0 > [ 460.789795] [<ffffffff8111b755>] ? thread_group_cputime+0x5/0x140 > [ 460.789800] [<ffffffff8111bbb9>] thread_group_cputime_adjusted+0x59/0x70 > [ 460.789810] [<ffffffff813179b5>] do_task_stat+0xc35/0xef0 > [ 460.789821] [<ffffffff8114306f>] ? __lock_acquire+0x3ff/0x1010 > [ 460.789827] [<ffffffff8114048d>] ? lock_release_holdtime+0x4d/0x270 > [ 460.789832] [<ffffffff81318a0c>] proc_tgid_stat+0x1c/0x30 > [ 460.789841] [<ffffffff813117db>] proc_single_show+0x7b/0xf0 > [ 460.789848] [<ffffffff812ace19>] seq_read+0x139/0x620 > [ 460.789857] [<ffffffff812894ae>] ? final_putname+0x2e/0x80 > [ 460.789866] [<ffffffff81278e4b>] vfs_read+0xdb/0x230 > [ 460.789871] [<ffffffff81279221>] sys_read+0x81/0xf0 > [ 460.789881] [<ffffffff819b3542>] system_call_fastpath+0x16/0x1b > [ 460.789883] ---[ end trace fbba451b40d2c6c7 ]--- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
