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Date: Mon, 15 Jun 2015 20:36:10 -0700
From: John Stultz <john.stultz@...aro.org>
To: Huang Ying <ying.huang@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>, LKP ML <lkp@...org>
Subject: Re: [lkp] [time] 78a0b9a793a: INFO: possible recursive locking
detected ]
On Mon, Jun 15, 2015 at 8:15 PM, Huang Ying <ying.huang@...el.com> wrote:
> FYI, we noticed the below changes on
>
> https://git.linaro.org/people/john.stultz/linux.git wip
> commit 78a0b9a793a36f73a9a3330dec00859e15d9ad6d ("time: Do leapsecond adjustment in gettime fastpaths")
>
>
> +------------------------------------------+------------+------------+
> | | 4ae9e1e25d | 78a0b9a793 |
> +------------------------------------------+------------+------------+
> | boot_successes | 900 | 263 |
> | boot_failures | 0 | 37 |
> | INFO:possible_recursive_locking_detected | 0 | 37 |
> | BUG:spinlock_lockup_suspected_on_CPU | 0 | 15 |
> | EIP_is_at_native_apic_mem_write | 0 | 15 |
> | EIP_is_at_read_seqcount_begin | 0 | 15 |
> | backtrace:SYSC_adjtimex | 0 | 32 |
> | backtrace:SyS_adjtimex | 0 | 32 |
> | backtrace:vfs_write | 0 | 7 |
> | backtrace:SyS_write | 0 | 7 |
> | BUG:kernel_test_hang | 0 | 22 |
> | backtrace:SYSC_clock_adjtime | 0 | 5 |
> | backtrace:SyS_clock_adjtime | 0 | 5 |
> | backtrace:lru_add_drain_all | 0 | 1 |
> | backtrace:SyS_mlock | 0 | 2 |
> | backtrace:do_group_exit | 0 | 1 |
> | backtrace:SyS_exit_group | 0 | 1 |
> | backtrace:cpu_startup_entry | 0 | 3 |
> | backtrace:__mm_populate | 0 | 1 |
> | backtrace:link_path_walk | 0 | 1 |
> | backtrace:path_init | 0 | 1 |
> | backtrace:do_sys_open | 0 | 1 |
> | backtrace:SyS_open | 0 | 1 |
> +------------------------------------------+------------+------------+
>
>
> [ 23.011400] VFS: Warning: trinity-c1 using old stat() call. Recompile your binary.
> [ 23.012387]
> [ 23.012580] =============================================
> [ 23.013218] [ INFO: possible recursive locking detected ]
> [ 23.013841] 4.1.0-rc5-01505-gd6201b6 #2 Not tainted
> [ 23.014419] ---------------------------------------------
> [ 23.015051] trinity-c1/22948 is trying to acquire lock:
> [ 23.015657] (tk_core){----..}, at: [<4107d71c>] timekeeping_get_ns+0x10/0xe8
> [ 23.016564]
> [ 23.016564] but task is already holding lock:
> [ 23.017241] (tk_core){----..}, at: [<4107f150>] do_adjtimex+0x58/0xc2
> [ 23.017380]
> [ 23.017380] other info that might help us debug this:
> [ 23.017380] Possible unsafe locking scenario:
> [ 23.017380]
> [ 23.017380] CPU0
> [ 23.017380] ----
> [ 23.017380] lock(tk_core);
> [ 23.017380] lock(tk_core);
> [ 23.017380]
> [ 23.017380] *** DEADLOCK ***
> [ 23.017380]
> [ 23.017380] May be due to missing lock nesting notation
> [ 23.017380]
> [ 23.017380] 2 locks held by trinity-c1/22948:
> [ 23.017380] #0: (timekeeper_lock){-.-...}, at: [<4107f144>] do_adjtimex+0x4c/0xc2
> [ 23.017380] #1: (tk_core){----..}, at: [<4107f150>] do_adjtimex+0x58/0xc2
> [ 23.017380]
> [ 23.017380] stack backtrace:
> [ 23.017380] CPU: 1 PID: 22948 Comm: trinity-c1 Not tainted 4.1.0-rc5-01505-gd6201b6 #2
> [ 23.017380] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [ 23.017380] 00000000 00000000 50211ddc 413ce68a 41c6a910 50211e50 410646c2 41551379
> [ 23.017380] 41551d81 4155126c 00000000 4fc09210 41c6a910 00001f02 00000000 7803e01f
> [ 23.017380] 00000000 4fc09210 00000000 00000002 4fc09238 4fc08d40 41c506f0 4fc09208
> [ 23.017380] Call Trace:
> [ 23.017380] [<413ce68a>] dump_stack+0x49/0x73
> [ 23.017380] [<410646c2>] __lock_acquire+0xb78/0xcd3
> [ 23.017380] [<4106414b>] ? __lock_acquire+0x601/0xcd3
> [ 23.017380] [<41064ad9>] lock_acquire+0x5b/0x7d
> [ 23.017380] [<4107d71c>] ? timekeeping_get_ns+0x10/0xe8
> [ 23.017380] [<4107d5f1>] read_seqcount_begin+0x2e/0x74
> [ 23.017380] [<4107d71c>] ? timekeeping_get_ns+0x10/0xe8
> [ 23.017380] [<4107d71c>] timekeeping_get_ns+0x10/0xe8
> [ 23.017380] [<4107f150>] ? do_adjtimex+0x58/0xc2
> [ 23.017380] [<4107dabf>] __getnstimeofday64_preleap+0x29/0x5d
> [ 23.017380] [<4107f158>] do_adjtimex+0x60/0xc2
> [ 23.017380] [<4107aa8e>] posix_clock_realtime_adj+0xa/0xc
> [ 23.017380] [<4107af8a>] SYSC_clock_adjtime+0x60/0x92
> [ 23.017380] [<4107b732>] SyS_clock_adjtime+0xe/0x10
> [ 23.017380] [<413d3aab>] syscall_call+0x7/0x7
> [ 23.017380] [<413d0000>] ? do_wait_for_common+0x69/0xe4
Yea. With CONFIG_DEBUG_TIMEKEEPING we take the seqlock again, so that
placement of __getnstimeofday64_preleap() - which didn't have the
external lock - inside the timekeeping lock was wrong.
I actually deleted that WIP branch last week, and reworked versions of
the patches (which shouldn't have this issue) have been included in
tip/timers/core. I still very much appreciate the extra testing being
done on my tree!
thanks
-john
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