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    Subject[next] possible recursive locking in autofs4_write
    Date
    Looks like mutex_lock should have been mutex_unlock in commit d668dc56
    (autofs4: deal with autofs4_write/autofs4_write races) at
    fs/autofs4/waitq.c:79, but I don't really know the code so if someone
    could have a look that would be great.

    Martin

    Lockdep info:
    Jan 15 01:54:08 callisto kernel: [21030.663616] =============================================
    Jan 15 01:54:08 callisto kernel: [21030.663618] [ INFO: possible recursive locking detected ]
    Jan 15 01:54:08 callisto kernel: [21030.663621] 3.2.0-next-20120113 #56 Not tainted
    Jan 15 01:54:08 callisto kernel: [21030.663623] ---------------------------------------------
    Jan 15 01:54:08 callisto kernel: [21030.663626] smoltSendProfil/7213 is trying to acquire lock:
    Jan 15 01:54:08 callisto kernel: [21030.663628] (&sbi->pipe_mutex){+.+.+.}, at: [<ffffffff812978fd>] autofs4_write+0xad/0x160 [fs/autofs4/waitq.c:81]
    Jan 15 01:54:08 callisto kernel: [21030.663640]
    Jan 15 01:54:08 callisto kernel: [21030.663641] but task is already holding lock:
    Jan 15 01:54:08 callisto kernel: [21030.663643] (&sbi->pipe_mutex){+.+.+.}, at: [<ffffffff812978b5>] autofs4_write+0x65/0x160 [fs/autofs4/waitq.c:74]
    Jan 15 01:54:08 callisto kernel: [21030.663650]
    Jan 15 01:54:08 callisto kernel: [21030.663650] other info that might help us debug this:
    Jan 15 01:54:08 callisto kernel: [21030.663652] Possible unsafe locking scenario:
    Jan 15 01:54:08 callisto kernel: [21030.663653]
    Jan 15 01:54:08 callisto kernel: [21030.663655] CPU0
    Jan 15 01:54:08 callisto kernel: [21030.663657] ----
    Jan 15 01:54:08 callisto kernel: [21030.663658] lock(&sbi->pipe_mutex);
    Jan 15 01:54:08 callisto kernel: [21030.663661] lock(&sbi->pipe_mutex);
    Jan 15 01:54:08 callisto kernel: [21030.663665]
    Jan 15 01:54:08 callisto kernel: [21030.663665] *** DEADLOCK ***
    Jan 15 01:54:08 callisto kernel: [21030.663666]
    Jan 15 01:54:08 callisto kernel: [21030.663668] May be due to missing lock nesting notation
    Jan 15 01:54:08 callisto kernel: [21030.663669]
    Jan 15 01:54:08 callisto kernel: [21030.663671] 1 lock held by smoltSendProfil/7213:
    Jan 15 01:54:08 callisto kernel: [21030.663673] #0: (&sbi->pipe_mutex){+.+.+.}, at: [<ffffffff812978b5>] autofs4_write+0x65/0x160
    Jan 15 01:54:08 callisto kernel: [21030.663681]
    Jan 15 01:54:08 callisto kernel: [21030.663681] stack backtrace:
    Jan 15 01:54:08 callisto kernel: [21030.663685] Pid: 7213, comm: smoltSendProfil Not tainted 3.2.0-next-20120113 #56
    Jan 15 01:54:08 callisto kernel: [21030.663687] Call Trace:
    Jan 15 01:54:08 callisto kernel: [21030.663693] [<ffffffff81089c61>] print_deadlock_bug+0xf1/0x100
    Jan 15 01:54:08 callisto kernel: [21030.663697] [<ffffffff8108b5e6>] validate_chain+0x646/0x780
    Jan 15 01:54:08 callisto kernel: [21030.663702] [<ffffffff8108d442>] __lock_acquire+0x392/0xa40
    Jan 15 01:54:08 callisto kernel: [21030.663706] [<ffffffff8108e1ce>] lock_acquire+0x9e/0x1f0
    Jan 15 01:54:08 callisto kernel: [21030.663709] [<ffffffff812978fd>] ? autofs4_write+0xad/0x160
    Jan 15 01:54:08 callisto kernel: [21030.663716] [<ffffffff817b576b>] mutex_lock_nested+0x6b/0x350
    Jan 15 01:54:08 callisto kernel: [21030.663720] [<ffffffff812978fd>] ? autofs4_write+0xad/0x160
    Jan 15 01:54:08 callisto kernel: [21030.663723] [<ffffffff812978fd>] autofs4_write+0xad/0x160
    Jan 15 01:54:08 callisto kernel: [21030.663727] [<ffffffff81297dfc>] autofs4_notify_daemon+0xfc/0x1d0
    Jan 15 01:54:08 callisto kernel: [21030.663731] [<ffffffff812983bf>] autofs4_wait+0x4ef/0x610
    Jan 15 01:54:08 callisto kernel: [21030.663735] [<ffffffff81296812>] ? autofs4_d_automount+0x182/0x2b0
    Jan 15 01:54:08 callisto kernel: [21030.663739] [<ffffffff8108df2b>] ? __lock_release+0x6b/0xe0
    Jan 15 01:54:08 callisto kernel: [21030.663742] [<ffffffff81296812>] ? autofs4_d_automount+0x182/0x2b0
    Jan 15 01:54:08 callisto kernel: [21030.663746] [<ffffffff81296416>] autofs4_mount_wait+0x36/0x50
    Jan 15 01:54:08 callisto kernel: [21030.663750] [<ffffffff8129681a>] autofs4_d_automount+0x18a/0x2b0
    Jan 15 01:54:08 callisto kernel: [21030.663756] [<ffffffff817a54ef>] follow_automount+0x85/0x103
    Jan 15 01:54:08 callisto kernel: [21030.663761] [<ffffffff81148952>] follow_managed+0xd2/0x130
    Jan 15 01:54:08 callisto kernel: [21030.663765] [<ffffffff8114adc1>] do_lookup+0x131/0x310
    Jan 15 01:54:08 callisto kernel: [21030.663769] [<ffffffff8114c714>] path_lookupat+0x114/0x770
    Jan 15 01:54:08 callisto kernel: [21030.663774] [<ffffffff81112ae0>] ? might_fault+0xa0/0xb0
    Jan 15 01:54:08 callisto kernel: [21030.663777] [<ffffffff81112a97>] ? might_fault+0x57/0xb0
    Jan 15 01:54:08 callisto kernel: [21030.663782] [<ffffffff8114cd9c>] do_path_lookup+0x2c/0xc0
    Jan 15 01:54:08 callisto kernel: [21030.663785] [<ffffffff8114d874>] user_path_at_empty+0x54/0xa0
    Jan 15 01:54:08 callisto kernel: [21030.663789] [<ffffffff81112ae0>] ? might_fault+0xa0/0xb0
    Jan 15 01:54:08 callisto kernel: [21030.663792] [<ffffffff81112a97>] ? might_fault+0x57/0xb0
    Jan 15 01:54:08 callisto kernel: [21030.663796] [<ffffffff81141d23>] ? cp_new_stat+0xf3/0x110
    Jan 15 01:54:08 callisto kernel: [21030.663800] [<ffffffff8114d8cc>] user_path_at+0xc/0x10
    Jan 15 01:54:08 callisto kernel: [21030.663805] [<ffffffff8116f942>] user_statfs+0x22/0x50
    Jan 15 01:54:08 callisto kernel: [21030.663809] [<ffffffff817c1747>] ? sysret_check+0x1b/0x56
    Jan 15 01:54:08 callisto kernel: [21030.663812] [<ffffffff8116f9db>] sys_statfs+0x1b/0x40
    Jan 15 01:54:08 callisto kernel: [21030.663816] [<ffffffff8108c087>] ? trace_hardirqs_on_caller+0x77/0x110
    Jan 15 01:54:08 callisto kernel: [21030.663821] [<ffffffff810b97ae>] ? audit_syscall_entry+0x30e/0x330
    Jan 15 01:54:08 callisto kernel: [21030.663826] [<ffffffff8139736e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
    Jan 15 01:54:08 callisto kernel: [21030.663830] [<ffffffff817c1722>] system_call_fastpath+0x16/0x1b


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