On Wednesday, October 20, 2010, PaweÅ Sikora wrote: > On Tuesday 19 October 2010 22:30:22 Rafael J. Wysocki wrote: > > On Tuesday, October 19, 2010, PaweÅ Sikora wrote: > > > On Monday 18 October 2010 23:36:51 Rafael J. Wysocki wrote: > > > > On Monday, October 18, 2010, PaweÅ Sikora wrote: > > > > > On Sunday 17 October 2010 22:21:48 Rafael J. Wysocki wrote: > > > > > > This message has been generated automatically as a part of a summary report > > > > > > of recent regressions. > > > > > > > > > > > > The following bug entry is on the current list of known regressions > > > > > > from 2.6.35. Please verify if it still should be listed and let the tracking team > > > > > > know (either way). > > > > > > > > > > hi, > > > > > > > > > > hot news from the front, recent tests on the pld-linux.org vendor kernel > > > > > show that the random task blocking in 2.6.35.7 during medium/heavy load (~4..25) > > > > > is related to the grsecurity patch. we'll forward problem report to the > > > > > grsec maintainer asap... > > > > > > > > So, to make things clear, this is not a mainline kernel issue, is it? > > > > > > i thought that was a grsecurity issue but now i have a testcase that > > > casues task blocking on my machine with the vanilla 2.6.35.7 kernel: > > > > > > steps to repoduce: > > > > > > on console 1: > > > - run 'make -j32' in kernel tree and wait several second for make forks > > > and medium system load (~15). > > > > > > on console 2: > > > - run 'sync' from root account to bump load more. > > > > > > on console 3: > > > - observe 'tail -f /var/log/kernel' for blocking issues. > > > > > > [ 360.517917] INFO: task sync:6712 blocked for more than 120 seconds. > > > [ 360.517920] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > [ 360.517922] sync D 00000000ffff4c7c 0 6712 2770 0x00000000 > > > [ 360.517926] ffff88021ac71d18 0000000000000086 ffff880200000000 0000000000004000 > > > [ 360.517930] 0000000000013700 0000000000013700 ffff88021ac71fd8 ffff88021ac71fd8 > > > [ 360.517933] ffff880205593020 0000000000013700 ffff88021ac71fd8 0000000000004000 > > > [ 360.517936] Call Trace: > > > [ 360.517944] [<ffffffff813b8dbd>] schedule_timeout+0x20d/0x2f0 > > > [ 360.517949] [<ffffffff8103baba>] ? enqueue_entity+0xea/0x170 > > > [ 360.517951] [<ffffffff8103bc09>] ? enqueue_task_fair+0x49/0x50 > > > [ 360.517954] [<ffffffff813b8945>] wait_for_common+0xc5/0x150 > > > [ 360.517957] [<ffffffff81040430>] ? default_wake_function+0x0/0x10 > > > [ 360.517959] [<ffffffff813b8a78>] wait_for_completion+0x18/0x20 > > > [ 360.517963] [<ffffffff8113b343>] sync_inodes_sb+0x83/0x170 > > > [ 360.517967] [<ffffffff8113f890>] ? sync_one_sb+0x0/0x20 > > > [ 360.517969] [<ffffffff8113f880>] __sync_filesystem+0x80/0x90 > > > [ 360.517972] [<ffffffff8113f8ab>] sync_one_sb+0x1b/0x20 > > > [ 360.517975] [<ffffffff8111d2c7>] iterate_supers+0x77/0xc0 > > > [ 360.517978] [<ffffffff8113f7bb>] sync_filesystems+0x1b/0x20 > > > [ 360.517980] [<ffffffff8113f92c>] sys_sync+0x1c/0x40 > > > [ 360.517984] [<ffffffff81002d6b>] system_call_fastpath+0x16/0x1b > > > > > > the 'make' is running on ext4 filesystem with underlying mdadm (raid10) > > > created from 2 caviar raid edition disks. the cpu is intel quad core > > > Q9300 with 8GB of ddr2 ram. > > > > So, how is this related to the original report? > > it's easier to reproduce on single test machine (no need to playing with parallel make and nfs). > in fact this isn't a 2.6.35.5->.7 regression but 2.6.34->2.6.35. the git-bisect found > first commit that introduces the 'sync' task blocking problem here: > > commit 7c8a3554c683f512dbcee26faedb42e4c05f12fa > Author: Jens Axboe <jens.axboe@xxxxxxxxxx> > Date: Tue May 18 14:29:29 2010 +0200 > > writeback: ensure that WB_SYNC_NONE writeback with sb pinned is sync > > Even if the writeout itself isn't a data integrity operation, we need > to ensure that the caller doesn't drop the sb umount sem before we > have actually done the writeback. > > This is a fixup for commit e913fc82. > > Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx> > > > i'll try to revert this patch from the 2.6.35.7 and test make+nfs in few days... OK, thanks. Jens added to the CC list. Rafael -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
