lkml.org 
[lkml]   [2009]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] tracing/events/lockdep: move tracepoints within recursive protection
* Steven Rostedt (rostedt@goodmis.org) wrote:
>
> Here's the dump that I get that triggers the lockdep warning:
>
> WARNING: at kernel/lockdep.c:2893 check_flags+0x1a7/0x1d0()
> Hardware name: Precision WorkStation 470
> Modules linked in: radeon drm autofs4 hidp rfcomm l2cap bluetooth sunrpc
>
> [snip]
>
> Pid: 3768, comm: sshd Not tainted 2.6.30-rc1 #1036
> Call Trace:
> [<ffffffff8025c321>] warn_slowpath+0xe1/0x110
> [<ffffffff80287f7c>] ? __lock_acquire+0x3ac/0xb20
> [<ffffffff80286dca>] ? validate_chain+0x4ca/0x12d0
> [<ffffffff80286dca>] ? validate_chain+0x4ca/0x12d0
> [<ffffffff80286dca>] ? validate_chain+0x4ca/0x12d0
> [<ffffffff80286dca>] ? validate_chain+0x4ca/0x12d0
> [<ffffffff80287f7c>] ? __lock_acquire+0x3ac/0xb20
> [<ffffffff8051a5a9>] ? __alloc_skb+0x49/0x160
> [<ffffffff80282407>] check_flags+0x1a7/0x1d0
> [<ffffffff80284d63>] lockdep_trace_alloc+0x33/0xe0
> [<ffffffff802f3682>] kmem_cache_alloc+0x32/0x160
> [<ffffffff8051a5a9>] __alloc_skb+0x49/0x160
> [<ffffffff8059192d>] tcp_send_ack+0x2d/0xe0
> [<ffffffff8058e941>] __tcp_ack_snd_check+0x61/0xb0
> [<ffffffff80590408>] tcp_rcv_established+0x398/0x600
> [<ffffffff80596a58>] tcp_v4_do_rcv+0x228/0x380
> [<ffffffff80228ed6>] ? ftrace_call+0x5/0x2b
> [<ffffffff8058454e>] ? tcp_prequeue_process+0x2e/0xa0
> [<ffffffff8058458d>] tcp_prequeue_process+0x6d/0xa0
> [<ffffffff8058734a>] tcp_recvmsg+0x49a/0x880
> [<ffffffff80514267>] sock_common_recvmsg+0x37/0x50
> [<ffffffff805116b9>] sock_aio_read+0x109/0x110
> [<ffffffff802f75f1>] do_sync_read+0xf1/0x130
> [<ffffffff8022ec33>] ? sched_clock+0x13/0x20
> [<ffffffff8022ec5d>] ? native_sched_clock+0x1d/0x50
> [<ffffffff802737d0>] ? autoremove_wake_function+0x0/0x40
> [<ffffffff80228ed6>] ? ftrace_call+0x5/0x2b
> [<ffffffff80381469>] ? cap_file_permission+0x9/0x10
> [<ffffffff80380116>] ? security_file_permission+0x16/0x20
> [<ffffffff802f7fc9>] vfs_read+0x159/0x170
> [<ffffffff802f8285>] sys_read+0x55/0x90
> [<ffffffff802291af>] system_call_fastpath+0x16/0x1b
> ---[ end trace 03d889e04bc7a9a7 ]---
> possible reason: unannotated irqs-on.
> irq event stamp: 12569
> hardirqs last enabled at (12567): [<ffffffff8026206a>] local_bh_enable+0xaa/0x110
> hardirqs last disabled at (12569): [<ffffffff80610c76>] int3+0x16/0x40
> softirqs last enabled at (12566): [<ffffffff80514d2b>] lock_sock_nested+0xfb/0x110
> softirqs last disabled at (12568): [<ffffffff8058454e>] tcp_prequeue_process+0x2e/0xa0
>
>
> Note, for some reason we hit int3 ??
>
> Tracepoints do not use int3 does it?
>

Not in your ftrace tree. My LTTng tree includes the immediate values,
which brienfly uses the int3 handler when enabling/disabling
tracepoints. But this seems unrelated to your problem.

> I have kprobes defined but not any kprobe self tests on.
>

Could this be a userspace breakpoint then ?

> Anyway, let me describe what the above is and what I found in my
> investigation.
>
> The lockdep took a check_flags error when it noticed that interrupts were
> enabled, but the current->hardirqs_enabled was 0. Lockdep thought
> interrupts were disabled but they were in fact enabled.
>
>
> The last 4 lines of the warning have the numbers in the parenthesis
> annotate the order of events: (Here they are in order)
>
> softirqs last enabled at (12566): [<ffffffff80514d2b>] lock_sock_nested+0xfb/0x110
> hardirqs last enabled at (12567): [<ffffffff8026206a>] local_bh_enable+0xaa/0x110
> softirqs last disabled at (12568): [<ffffffff8058454e>] tcp_prequeue_process+0x2e/0xa0
> hardirqs last disabled at (12569): [<ffffffff80610c76>] int3+0x16/0x40
>
> The last change that lockdep saw was interrupts being disabled by int3. I
> still don't understand why int3 was enabled. I have startup tests for
> ftrace and the event tracer, but this blob happened when I first ssh'd
> into the box.

Also note that maybe some entry.S annotation could be missing, making
kallsyms think it was running within int3 when in fact it was running in
a different function. I would double-check with objdump givin the
ffffffff80610c76 address to make sure.
Just giving my 2 cents before going to bed. I don't have any more brain
left for tonight.

Cheers,

Mathieu

>
> In arch/x86/kernel/entry_64.S we have:
>
> paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
>
> .macro paranoidzeroentry sym do_sym
> ENTRY(\sym)
> INTR_FRAME
> PARAVIRT_ADJUST_EXCEPTION_FRAME
> pushq $-1 /* ORIG_RAX: no syscall to restart */
> CFI_ADJUST_CFA_OFFSET 8
> subq $15*8, %rsp
> call save_paranoid
> TRACE_IRQS_OFF
> movq %rsp,%rdi /* pt_regs pointer */
> xorl %esi,%esi /* no error code */
> call \do_sym
> jmp paranoid_exit /* %ebx: no swapgs flag */
> CFI_ENDPROC
> END(\sym)
> .endm
>
>
> ENTRY(paranoid_exit)
> INTR_FRAME
> DISABLE_INTERRUPTS(CLBR_NONE)
> TRACE_IRQS_OFF
> testl %ebx,%ebx /* swapgs needed? */
> jnz paranoid_restore
> testl $3,CS(%rsp)
> jnz paranoid_userspace
> paranoid_swapgs:
> TRACE_IRQS_IRETQ 0
> SWAPGS_UNSAFE_STACK
> paranoid_restore:
> RESTORE_ALL 8
> jmp irq_return
>
>
> irq_return:
> INTERRUPT_RETURN
>
>
> INTERRUPT_RETURN is simply defined as iretq
>
>
> I see that we call TRACE_IRQS_OFF when entering paranoid_exit, but if we
> do not need to swapgs (we don't because int3 looks like it happened in
> kernel space) we just call irq_return and jump back. We miss the fact that
> the irq_return enables interrupts for us.
>
> I'd try to come up with a fix, but this gets a bit complex, and I figured
> I let the lockdep irq-tracing guru's play with this magic. I'm just
> reporting the problem ;-)
>
> -- Steve
>

--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


\
 
 \ /
  Last update: 2009-04-17 06:55    [W:0.152 / U:0.400 seconds]
©2003-2014 Jasper Spaans. Advertise on this site