| Message ID | 20201218185032.2464558-2-jonathan.lemon@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | bpf: increment and use correct thread iterator | expand |
On 12/18/20 10:01 PM, Andrii Nakryiko wrote: > On Fri, Dec 18, 2020 at 12:47 PM Jonathan Lemon > <jonathan.lemon@gmail.com> wrote: >> >> From: Jonathan Lemon <bsd@fb.com> >> >> On some systems, some variant of the following splat is >> repeatedly seen. The common factor in all traces seems >> to be the entry point to task_file_seq_next(). With the >> patch, all warnings go away. >> >> rcu: INFO: rcu_sched self-detected stall on CPU >> rcu: \x0926-....: (20992 ticks this GP) idle=d7e/1/0x4000000000000002 softirq=81556231/81556231 fqs=4876 >> \x09(t=21033 jiffies g=159148529 q=223125) >> NMI backtrace for cpu 26 >> CPU: 26 PID: 2015853 Comm: bpftool Kdump: loaded Not tainted 5.6.13-0_fbk4_3876_gd8d1f9bf80bb #1 >> Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A12 10/08/2018 >> Call Trace: >> <IRQ> >> dump_stack+0x50/0x70 >> nmi_cpu_backtrace.cold.6+0x13/0x50 >> ? lapic_can_unplug_cpu.cold.30+0x40/0x40 >> nmi_trigger_cpumask_backtrace+0xba/0xca >> rcu_dump_cpu_stacks+0x99/0xc7 >> rcu_sched_clock_irq.cold.90+0x1b4/0x3aa >> ? tick_sched_do_timer+0x60/0x60 >> update_process_times+0x24/0x50 >> tick_sched_timer+0x37/0x70 >> __hrtimer_run_queues+0xfe/0x270 >> hrtimer_interrupt+0xf4/0x210 >> smp_apic_timer_interrupt+0x5e/0x120 >> apic_timer_interrupt+0xf/0x20 >> </IRQ> >> RIP: 0010:get_pid_task+0x38/0x80 >> Code: 89 f6 48 8d 44 f7 08 48 8b 00 48 85 c0 74 2b 48 83 c6 55 48 c1 e6 04 48 29 f0 74 19 48 8d 78 20 ba 01 00 00 00 f0 0f c1 50 20 <85> d2 74 27 78 11 83 c2 01 78 0c 48 83 c4 08 c3 31 c0 48 83 c4 08 >> RSP: 0018:ffffc9000d293dc8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 >> RAX: ffff888637c05600 RBX: ffffc9000d293e0c RCX: 0000000000000000 >> RDX: 0000000000000001 RSI: 0000000000000550 RDI: ffff888637c05620 >> RBP: ffffffff8284eb80 R08: ffff88831341d300 R09: ffff88822ffd8248 >> R10: ffff88822ffd82d0 R11: 00000000003a93c0 R12: 0000000000000001 >> R13: 00000000ffffffff R14: ffff88831341d300 R15: 0000000000000000 >> ? find_ge_pid+0x1b/0x20 >> task_seq_get_next+0x52/0xc0 >> task_file_seq_get_next+0x159/0x220 >> task_file_seq_next+0x4f/0xa0 >> bpf_seq_read+0x159/0x390 >> vfs_read+0x8a/0x140 >> ksys_read+0x59/0xd0 >> do_syscall_64+0x42/0x110 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> RIP: 0033:0x7f95ae73e76e >> Code: Bad RIP value. >> RSP: 002b:00007ffc02c1dbf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 >> RAX: ffffffffffffffda RBX: 000000000170faa0 RCX: 00007f95ae73e76e >> RDX: 0000000000001000 RSI: 00007ffc02c1dc30 RDI: 0000000000000007 >> RBP: 00007ffc02c1ec70 R08: 0000000000000005 R09: 0000000000000006 >> R10: fffffffffffff20b R11: 0000000000000246 R12: 00000000019112a0 >> R13: 0000000000000000 R14: 0000000000000007 R15: 00000000004283c0 >> >> If unable to obtain the file structure for the current task, >> proceed to the next task number after the one returned from >> task_seq_get_next(), instead of the next task number from the >> original iterator. >> >> Also, save the stopping task number from task_seq_get_next() >> on failure in case of restarts. >> >> Fixes: a650da2ee52a ("bpf: Add task and task/file iterator targets") Commit sha is non-existent, I fixed it up. Took first 2 into bpf given first in particular is a fix. Please submit 3/3 individually once we synced trees back. >> Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com> >> --- > > LGTM, thanks! > > Acked-by: Andrii Nakryiko <andrii@kernel.org>
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 0458a40edf10..8033ab19138a 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -158,13 +158,14 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info) if (!curr_task) { info->task = NULL; info->files = NULL; + info->tid = curr_tid; return NULL; } curr_files = get_files_struct(curr_task); if (!curr_files) { put_task_struct(curr_task); - curr_tid = ++(info->tid); + curr_tid = curr_tid + 1; info->fd = 0; goto again; }