* [syzbot] WARNING: suspicious RCU usage in get_signal @ 2021-05-06 21:34 syzbot 2021-05-07 8:37 ` Peter Zijlstra 0 siblings, 1 reply; 6+ messages in thread From: syzbot @ 2021-05-06 21:34 UTC (permalink / raw) To: axboe, christian, ebiederm, linux-kernel, oleg, pcc, peterz, syzkaller-bugs, tglx Hello, syzbot found the following issue on: HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d userspace arch: i386 Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com ============================= WARNING: suspicious RCU usage 5.12.0-syzkaller #0 Not tainted ----------------------------- kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 0 no locks held by syz-executor.4/10430. stack backtrace: CPU: 0 PID: 10430 Comm: syz-executor.4 Not tainted 5.12.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x141/0x1d7 lib/dump_stack.c:120 ___might_sleep+0x266/0x2c0 kernel/sched/core.c:8304 try_to_freeze_unsafe include/linux/freezer.h:57 [inline] try_to_freeze include/linux/freezer.h:67 [inline] get_signal+0x14a/0x2150 kernel/signal.c:2613 arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:789 handle_signal_work kernel/entry/common.c:147 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x171/0x280 kernel/entry/common.c:208 irqentry_exit_to_user_mode+0x5/0x40 kernel/entry/common.c:314 exc_page_fault+0xc6/0x180 arch/x86/mm/fault.c:1534 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577 RIP: 0023:0x8052207 Code: 0c 50 e8 ac 5a 01 00 83 c4 10 85 c0 0f 84 b9 01 00 00 65 f0 83 2d d8 ff ff ff 01 8b 5c 24 08 e8 6f f7 00 00 8b 4c 24 0c 8b 00 <8b> 71 50 89 41 54 85 c0 75 05 83 fe ff 74 19 6b 44 24 1c 34 8b 4c RSP: 002b:00000000f5514640 EFLAGS: 00010283 RAX: 000000000000000e RBX: 0000000000000000 RCX: 0000000000000000 RDX: 00000000080521e4 RSI: 0000000000000005 RDI: 00000000080ea51d RBP: 000000000819afc0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING: suspicious RCU usage in get_signal 2021-05-06 21:34 [syzbot] WARNING: suspicious RCU usage in get_signal syzbot @ 2021-05-07 8:37 ` Peter Zijlstra 2021-05-07 8:42 ` Dmitry Vyukov 0 siblings, 1 reply; 6+ messages in thread From: Peter Zijlstra @ 2021-05-07 8:37 UTC (permalink / raw) To: syzbot Cc: axboe, christian, ebiederm, linux-kernel, oleg, pcc, syzkaller-bugs, tglx, Paul McKenney On Thu, May 06, 2021 at 02:34:27PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe > dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this issue yet. > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com > > ============================= > WARNING: suspicious RCU usage > 5.12.0-syzkaller #0 Not tainted > ----------------------------- > kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! > > other info that might help us debug this: > > > rcu_scheduler_active = 2, debug_locks = 0 > no locks held by syz-executor.4/10430. Looks like this is a concurrent fail?, if !debug_locks (as per the above) then RCU_LOCKDEP_WARN() should not trigger. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING: suspicious RCU usage in get_signal 2021-05-07 8:37 ` Peter Zijlstra @ 2021-05-07 8:42 ` Dmitry Vyukov 2021-05-07 17:19 ` Paul E. McKenney 0 siblings, 1 reply; 6+ messages in thread From: Dmitry Vyukov @ 2021-05-07 8:42 UTC (permalink / raw) To: Peter Zijlstra Cc: syzbot, Jens Axboe, Christian Brauner, Eric W. Biederman, LKML, Oleg Nesterov, Peter Collingbourne, syzkaller-bugs, Thomas Gleixner, Paul McKenney On Fri, May 7, 2021 at 10:38 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, May 06, 2021 at 02:34:27PM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe > > dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d > > userspace arch: i386 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com > > > > ============================= > > WARNING: suspicious RCU usage > > 5.12.0-syzkaller #0 Not tainted > > ----------------------------- > > kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! > > > > other info that might help us debug this: > > > > > > rcu_scheduler_active = 2, debug_locks = 0 > > no locks held by syz-executor.4/10430. > > Looks like this is a concurrent fail?, if !debug_locks (as per the above) > then RCU_LOCKDEP_WARN() should not trigger. FTR the log is here: https://syzkaller.appspot.com/text?tag=CrashLog&x=123a56a5d00000 It contains 2 intermixed reports: [ 289.896033][T10430] ============================= [ 289.896039][T10430] WARNING: suspicious RCU usage [ 289.896046][T10430] 5.12.0-syzkaller #0 Not tainted [ 289.898388][T13493] ====================================================== [ 289.898401][T13493] WARNING: possible circular locking dependency detected [ 289.898410][T13493] 5.12.0-syzkaller #0 Not tainted [ 289.898424][T13493] ------------------------------------------------------ [ 289.898432][T13493] syz-executor.0/13493 is trying to acquire lock: [ 289.898448][T13493] ffff888019065ca0 (&bdev->bd_mutex){+.+.}-{3:3}, at: del_gendisk+0x250/0x9e0 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING: suspicious RCU usage in get_signal 2021-05-07 8:42 ` Dmitry Vyukov @ 2021-05-07 17:19 ` Paul E. McKenney 2021-05-08 5:03 ` Dmitry Vyukov 0 siblings, 1 reply; 6+ messages in thread From: Paul E. McKenney @ 2021-05-07 17:19 UTC (permalink / raw) To: Dmitry Vyukov Cc: Peter Zijlstra, syzbot, Jens Axboe, Christian Brauner, Eric W. Biederman, LKML, Oleg Nesterov, Peter Collingbourne, syzkaller-bugs, Thomas Gleixner On Fri, May 07, 2021 at 10:42:48AM +0200, Dmitry Vyukov wrote: > On Fri, May 7, 2021 at 10:38 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Thu, May 06, 2021 at 02:34:27PM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe > > > dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d > > > userspace arch: i386 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com > > > > > > ============================= > > > WARNING: suspicious RCU usage > > > 5.12.0-syzkaller #0 Not tainted > > > ----------------------------- > > > kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! > > > > > > other info that might help us debug this: > > > > > > > > > rcu_scheduler_active = 2, debug_locks = 0 > > > no locks held by syz-executor.4/10430. > > > > Looks like this is a concurrent fail?, if !debug_locks (as per the above) > > then RCU_LOCKDEP_WARN() should not trigger. > > FTR the log is here: > https://syzkaller.appspot.com/text?tag=CrashLog&x=123a56a5d00000 > > It contains 2 intermixed reports: > > [ 289.896033][T10430] ============================= > [ 289.896039][T10430] WARNING: suspicious RCU usage > [ 289.896046][T10430] 5.12.0-syzkaller #0 Not tainted > [ 289.898388][T13493] ====================================================== > [ 289.898401][T13493] WARNING: possible circular locking dependency detected > [ 289.898410][T13493] 5.12.0-syzkaller #0 Not tainted > [ 289.898424][T13493] ------------------------------------------------------ > [ 289.898432][T13493] syz-executor.0/13493 is trying to acquire lock: > [ 289.898448][T13493] ffff888019065ca0 (&bdev->bd_mutex){+.+.}-{3:3}, > at: del_gendisk+0x250/0x9e0 This "suspicious RCU usage" false positive looks to be addressed by this commit in -rcu, slated for the v5.14 merge window: 81a5e05455d4 ("rcu: Reject RCU_LOCKDEP_WARN() false positives") So I suggest ignoring the "suspicious RCU usage" report in favor of the "possible circular locking dependency detected" report. Thanx, Paul ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING: suspicious RCU usage in get_signal 2021-05-07 17:19 ` Paul E. McKenney @ 2021-05-08 5:03 ` Dmitry Vyukov 2021-05-08 22:59 ` Paul E. McKenney 0 siblings, 1 reply; 6+ messages in thread From: Dmitry Vyukov @ 2021-05-08 5:03 UTC (permalink / raw) To: Paul E. McKenney Cc: Peter Zijlstra, syzbot, Jens Axboe, Christian Brauner, Eric W. Biederman, LKML, Oleg Nesterov, Peter Collingbourne, syzkaller-bugs, Thomas Gleixner On Fri, May 7, 2021 at 7:19 PM Paul E. McKenney <paulmck@kernel.org> wrote: > > On Fri, May 07, 2021 at 10:42:48AM +0200, Dmitry Vyukov wrote: > > On Fri, May 7, 2021 at 10:38 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > On Thu, May 06, 2021 at 02:34:27PM -0700, syzbot wrote: > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... > > > > git tree: upstream > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d > > > > userspace arch: i386 > > > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com > > > > > > > > ============================= > > > > WARNING: suspicious RCU usage > > > > 5.12.0-syzkaller #0 Not tainted > > > > ----------------------------- > > > > kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! > > > > > > > > other info that might help us debug this: > > > > > > > > > > > > rcu_scheduler_active = 2, debug_locks = 0 > > > > no locks held by syz-executor.4/10430. > > > > > > Looks like this is a concurrent fail?, if !debug_locks (as per the above) > > > then RCU_LOCKDEP_WARN() should not trigger. > > > > FTR the log is here: > > https://syzkaller.appspot.com/text?tag=CrashLog&x=123a56a5d00000 > > > > It contains 2 intermixed reports: > > > > [ 289.896033][T10430] ============================= > > [ 289.896039][T10430] WARNING: suspicious RCU usage > > [ 289.896046][T10430] 5.12.0-syzkaller #0 Not tainted > > [ 289.898388][T13493] ====================================================== > > [ 289.898401][T13493] WARNING: possible circular locking dependency detected > > [ 289.898410][T13493] 5.12.0-syzkaller #0 Not tainted > > [ 289.898424][T13493] ------------------------------------------------------ > > [ 289.898432][T13493] syz-executor.0/13493 is trying to acquire lock: > > [ 289.898448][T13493] ffff888019065ca0 (&bdev->bd_mutex){+.+.}-{3:3}, > > at: del_gendisk+0x250/0x9e0 > > This "suspicious RCU usage" false positive looks to be addressed by this > commit in -rcu, slated for the v5.14 merge window: > > 81a5e05455d4 ("rcu: Reject RCU_LOCKDEP_WARN() false positives") > > So I suggest ignoring the "suspicious RCU usage" report in favor of the > "possible circular locking dependency detected" report. Oh, I see, it's not merged yet. In my memory we discussed it so long ago that I assumed it is fixed already. Let's mark it as fixed then: #syz fix: rcu: Reject RCU_LOCKDEP_WARN() false positives Thanks for double checking. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] WARNING: suspicious RCU usage in get_signal 2021-05-08 5:03 ` Dmitry Vyukov @ 2021-05-08 22:59 ` Paul E. McKenney 0 siblings, 0 replies; 6+ messages in thread From: Paul E. McKenney @ 2021-05-08 22:59 UTC (permalink / raw) To: Dmitry Vyukov Cc: Peter Zijlstra, syzbot, Jens Axboe, Christian Brauner, Eric W. Biederman, LKML, Oleg Nesterov, Peter Collingbourne, syzkaller-bugs, Thomas Gleixner On Sat, May 08, 2021 at 07:03:51AM +0200, Dmitry Vyukov wrote: > On Fri, May 7, 2021 at 7:19 PM Paul E. McKenney <paulmck@kernel.org> wrote: > > > > On Fri, May 07, 2021 at 10:42:48AM +0200, Dmitry Vyukov wrote: > > > On Fri, May 7, 2021 at 10:38 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > > > On Thu, May 06, 2021 at 02:34:27PM -0700, syzbot wrote: > > > > > Hello, > > > > > > > > > > syzbot found the following issue on: > > > > > > > > > > HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel... > > > > > git tree: upstream > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000 > > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d > > > > > userspace arch: i386 > > > > > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > > Reported-by: syzbot+37fc8b84ffa2279d636d@syzkaller.appspotmail.com > > > > > > > > > > ============================= > > > > > WARNING: suspicious RCU usage > > > > > 5.12.0-syzkaller #0 Not tainted > > > > > ----------------------------- > > > > > kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section! > > > > > > > > > > other info that might help us debug this: > > > > > > > > > > > > > > > rcu_scheduler_active = 2, debug_locks = 0 > > > > > no locks held by syz-executor.4/10430. > > > > > > > > Looks like this is a concurrent fail?, if !debug_locks (as per the above) > > > > then RCU_LOCKDEP_WARN() should not trigger. > > > > > > FTR the log is here: > > > https://syzkaller.appspot.com/text?tag=CrashLog&x=123a56a5d00000 > > > > > > It contains 2 intermixed reports: > > > > > > [ 289.896033][T10430] ============================= > > > [ 289.896039][T10430] WARNING: suspicious RCU usage > > > [ 289.896046][T10430] 5.12.0-syzkaller #0 Not tainted > > > [ 289.898388][T13493] ====================================================== > > > [ 289.898401][T13493] WARNING: possible circular locking dependency detected > > > [ 289.898410][T13493] 5.12.0-syzkaller #0 Not tainted > > > [ 289.898424][T13493] ------------------------------------------------------ > > > [ 289.898432][T13493] syz-executor.0/13493 is trying to acquire lock: > > > [ 289.898448][T13493] ffff888019065ca0 (&bdev->bd_mutex){+.+.}-{3:3}, > > > at: del_gendisk+0x250/0x9e0 > > > > This "suspicious RCU usage" false positive looks to be addressed by this > > commit in -rcu, slated for the v5.14 merge window: > > > > 81a5e05455d4 ("rcu: Reject RCU_LOCKDEP_WARN() false positives") > > > > So I suggest ignoring the "suspicious RCU usage" report in favor of the > > "possible circular locking dependency detected" report. > > Oh, I see, it's not merged yet. > In my memory we discussed it so long ago that I assumed it is fixed already. It was a bit too late to make my pull request. I won't lose it. ;-) Thanx, Paul > Let's mark it as fixed then: > > #syz fix: rcu: Reject RCU_LOCKDEP_WARN() false positives > > Thanks for double checking. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-05-08 22:59 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-05-06 21:34 [syzbot] WARNING: suspicious RCU usage in get_signal syzbot 2021-05-07 8:37 ` Peter Zijlstra 2021-05-07 8:42 ` Dmitry Vyukov 2021-05-07 17:19 ` Paul E. McKenney 2021-05-08 5:03 ` Dmitry Vyukov 2021-05-08 22:59 ` Paul E. McKenney
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