Messages in this thread | | | From | Dmitry Vyukov <> | Date | Sat, 8 May 2021 07:03:51 +0200 | Subject | Re: [syzbot] WARNING: suspicious RCU usage in get_signal |
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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.
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