Messages in this thread | | | Date | Wed, 27 Mar 2019 08:34:05 +0100 | From | Juri Lelli <> | Subject | Re: [PATCH] sched/deadline: correctly handle active 0-lag timers |
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Hi,
On 25/03/19 14:15, luca abeni wrote: > syzbot reported the following warning: > [ 948.126369] WARNING: CPU: 4 PID: 17089 at kernel/sched/deadline.c:255 task_non_contending+0xae0/0x1950 > [ 948.130198] Kernel panic - not syncing: panic_on_warn set ... > [ 948.130198] > [ 948.134221] CPU: 4 PID: 17089 Comm: syz-executor.1 Not tainted 4.19.27 #2 > [ 948.139072] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 > [ 948.141603] Call Trace: > [ 948.142277] dump_stack+0xca/0x13e > [ 948.164636] panic+0x1f7/0x543 > [ 948.168704] ? refcount_error_report+0x29d/0x29d > [ 948.172438] ? __warn+0x1d1/0x210 > [ 948.183359] ? task_non_contending+0xae0/0x1950 > [ 948.191747] __warn+0x1ec/0x210 > [ 948.196276] ? task_non_contending+0xae0/0x1950 > [ 948.202476] report_bug+0x1ee/0x2b0 > [ 948.204622] fixup_bug.part.7+0x37/0x80 > [ 948.206879] do_error_trap+0x22c/0x290 > [ 948.211340] ? math_error+0x2f0/0x2f0 > [ 948.217033] ? trace_hardirqs_off_caller+0x40/0x190 > [ 948.222477] ? trace_hardirqs_off_thunk+0x1a/0x1c > [ 948.229877] invalid_op+0x14/0x20 > [ 948.238317] RIP: 0010:task_non_contending+0xae0/0x1950 > [ 948.253825] Code: 6d 29 83 48 89 4c 24 20 48 89 54 24 10 c6 05 d0 89 > 5a 03 01 e8 11 ea ee ff 0f 0b 48 8b 4c 24 20 48 8b 54 24 10 e9 bb f7 ff > ff <0f> 0b e9 1d f6 ff ff e8 d4 a7 09 00 85 c0 0f 85 74 f8 ff ff 48 c7 > [ 948.272329] RSP: 0018:ffff8883d443f8c0 EFLAGS: 00010002 > [ 948.293045] RAX: 0000000000000001 RBX: ffff8883d3572468 RCX: ffffffff813a6571 > [ 948.300323] RDX: 00000000000008ab RSI: ffffc900030e4000 RDI: ffff8883e2fe6278 > [ 948.305278] RBP: ffff8883e2f00000 R08: ffffed1078ea3ab2 R09: ffffed1078ea3ab2 > [ 948.316441] R10: 0000000000000001 R11: ffffed1078ea3ab1 R12: 000000000002c680 > [ 948.320257] R13: ffff8883d357217c R14: 0000000000000001 R15: ffff8883d3572140 > [ 948.324500] ? hrtimer_active+0x171/0x1f0 > [ 948.327421] ? dequeue_task_dl+0x38/0x970 > [ 948.330572] __schedule+0x94b/0x1a80 > [ 948.333578] ? __sched_text_start+0x8/0x8 > [ 948.336141] ? lock_downgrade+0x5e0/0x5e0 > [ 948.338111] ? plist_add+0x23e/0x480 > [ 948.339706] schedule+0x7c/0x1a0 > [ 948.341395] futex_wait_queue_me+0x319/0x600 > [ 948.343329] ? get_futex_key_refs+0xd0/0xd0 > [ 948.345037] ? lock_downgrade+0x5e0/0x5e0 > [ 948.347206] ? get_futex_key_refs+0xa4/0xd0 > [ 948.353007] futex_wait+0x1e7/0x590 > [ 948.355328] ? futex_wait_setup+0x2b0/0x2b0 > [ 948.360578] ? __lock_acquire+0x60c/0x3b70 > [ 948.369186] ? __save_stack_trace+0x92/0x100 > [ 948.374344] ? hash_futex+0x15/0x210 > [ 948.376832] ? drop_futex_key_refs+0x3c/0xd0 > [ 948.378591] ? futex_wake+0x14e/0x450 > [ 948.381609] do_futex+0x5c9/0x15e0 > [ 948.384567] ? perf_syscall_enter+0xb1/0xc80 > [ 948.390307] ? exit_robust_list+0x240/0x240 > [ 948.393566] ? ftrace_syscall_exit+0x5c0/0x5c0 > [ 948.396369] ? lock_downgrade+0x5e0/0x5e0 > [ 948.401748] ? __might_fault+0x17c/0x1c0 > [ 948.404171] __x64_sys_futex+0x296/0x380 > [ 948.406472] ? __ia32_sys_futex+0x370/0x370 > [ 948.440630] ? trace_hardirqs_on_thunk+0x1a/0x1c > [ 948.441774] ? trace_hardirqs_off_caller+0x40/0x190 > [ 948.442770] ? do_syscall_64+0x3b/0x580 > [ 948.486728] do_syscall_64+0xc8/0x580 > [ 948.489138] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [ 948.492072] RIP: 0033:0x462eb9 > [ 948.492788] Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 > 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f > 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 > [ 948.532016] RSP: 002b:00007f7ac8a67cd8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca > [ 948.536811] RAX: ffffffffffffffda RBX: 000000000073bf08 RCX: 0000000000462eb9 > [ 948.542138] RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08 > [ 948.548077] RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 > [ 948.562535] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c > [ 948.569184] R13: 0000000000000000 R14: 000000000073bf00 R15: 00007fff106d8c10
Not sure if this stack needs a bit of cleaning for the changelog (Code: seems mangled as well).
> line 255 of deadline.c is > WARN_ON(hrtimer_active(&dl_se->inactive_timer)); > in task_non_contending(). > Unfortunately, in some cases (for example, a deadline task > continuosly blocking and waking immediately) it can happen that > a task blocks (and task_non_contending() is called) while the > 0-lag timer is still active. In this case, the safest thing to > do is to immediately decrease the running bandwidth of the task, > without trying to re-arm the 0-lag timer. > > Signed-off-by: luca abeni <luca.abeni@santannapisa.it>
But I could verify that this fixes the issue I was also able to reproduce.
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Thanks!
- Juri
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