From: Steven Rostedt <rostedt@goodmis.org>
To: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: tglx@linutronix.de, mhiramat@kernel.org, namhyung@kernel.org,
vedang.patel@intel.com, bigeasy@linutronix.de,
joel.opensrc@gmail.com, joelaf@google.com,
mathieu.desnoyers@efficios.com, baohong.liu@intel.com,
linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Subject: Re: [PATCH v2 35/40] tracing: Reverse the order event_mutex/trace_types_lock are taken
Date: Fri, 8 Sep 2017 15:41:36 -0400 [thread overview]
Message-ID: <20170908154136.096d49ff@gandalf.local.home> (raw)
In-Reply-To: <20170908153135.14725f01@gandalf.local.home>
On Fri, 8 Sep 2017 15:31:35 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 5 Sep 2017 16:57:47 -0500
> Tom Zanussi <tom.zanussi@linux.intel.com> wrote:
>
> > Change the order event_mutex and trace_types_lock are taken, to avoid
> > circular dependencies and lockdep spew.
> >
> > Changing the order shouldn't matter to any current code, but does to
> > anything that takes the event_mutex first and then trace_types_lock.
> > This is the case when calling tracing_set_clock from inside an event
> > command, which already holds the event_mutex.
>
> This is a very scary patch. I'll apply it and run a bunch of tests with
> lockdep enabled. Let's see what blows up (or not).
Boom!
======================================================
WARNING: possible circular locking dependency detected
4.13.0-rc7-test+ #84 Not tainted
------------------------------------------------------
mkdir/1674 is trying to acquire lock:
(event_mutex){+.+.+.}, at: [<ffffffff811b18bd>] event_trace_add_tracer+0x1d/0xb0
but task is already holding lock:
(trace_types_lock){+.+.+.}, at: [<ffffffff811a121f>] instance_mkdir+0x2f/0x250
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (trace_types_lock){+.+.+.}:
lock_acquire+0xe3/0x1d0
__mutex_lock+0x81/0x950
mutex_lock_nested+0x1b/0x20
trace_module_notify+0x33/0x1b0
notifier_call_chain+0x4a/0x70
__blocking_notifier_call_chain+0x4d/0x70
blocking_notifier_call_chain+0x16/0x20
load_module+0x21df/0x2dd0
SYSC_finit_module+0xbc/0xf0
SyS_finit_module+0xe/0x10
do_syscall_64+0x62/0x140
return_from_SYSCALL_64+0x0/0x7a
-> #0 (event_mutex){+.+.+.}:
__lock_acquire+0x1026/0x11d0
lock_acquire+0xe3/0x1d0
__mutex_lock+0x81/0x950
mutex_lock_nested+0x1b/0x20
event_trace_add_tracer+0x1d/0xb0
instance_mkdir+0x173/0x250
tracefs_syscall_mkdir+0x40/0x70
vfs_mkdir+0xfb/0x190
SyS_mkdir+0x6b/0xd0
entry_SYSCALL_64_fastpath+0x1f/0xbe
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(trace_types_lock);
lock(event_mutex);
lock(trace_types_lock);
lock(event_mutex);
*** DEADLOCK ***
2 locks held by mkdir/1674:
#0: (sb_writers#10){.+.+.+}, at: [<ffffffff812b4824>] mnt_want_write+0x24/0x50
#1: (trace_types_lock){+.+.+.}, at: [<ffffffff811a121f>] instance_mkdir+0x2f/0x250
stack backtrace:
CPU: 3 PID: 1674 Comm: mkdir Not tainted 4.13.0-rc7-test+ #84
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
Call Trace:
dump_stack+0x86/0xcf
print_circular_bug+0x1be/0x210
__lock_acquire+0x1026/0x11d0
lock_acquire+0xe3/0x1d0
? lock_acquire+0xe3/0x1d0
? event_trace_add_tracer+0x1d/0xb0
? event_trace_add_tracer+0x1d/0xb0
__mutex_lock+0x81/0x950
? event_trace_add_tracer+0x1d/0xb0
? event_trace_add_tracer+0x1d/0xb0
? __create_dir+0xcb/0x130
mutex_lock_nested+0x1b/0x20
? mutex_lock_nested+0x1b/0x20
event_trace_add_tracer+0x1d/0xb0
instance_mkdir+0x173/0x250
tracefs_syscall_mkdir+0x40/0x70
? tracefs_syscall_mkdir+0x40/0x70
vfs_mkdir+0xfb/0x190
SyS_mkdir+0x6b/0xd0
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x7f4867afa947
RSP: 002b:00007ffd3dc35c08 EFLAGS: 00000202 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f4867afa947
RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007ffd3dc3764f
RBP: ffffc90000f2ff98 R08: 00000000000001ff R09: 000055f96a551ac0
R10: 000055f96b700010 R11: 0000000000000202 R12: 0000000000000001
R13: 00007ffd3dc35f28 R14: 00000000000001ff R15: ffffffff8189316a
? entry_SYSCALL_64_after_swapgs+0x17/0x4f
It appears to be caused by instance creation. I'll look at that.
-- Steve
next prev parent reply other threads:[~2017-09-08 19:41 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-05 21:57 [PATCH v2 00/40] tracing: Inter-event (e.g. latency) support Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 01/40] tracing: Exclude 'generic fields' from histograms Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 02/40] tracing: Add support to detect and avoid duplicates Tom Zanussi
2017-09-06 18:32 ` Steven Rostedt
2017-09-06 18:47 ` Steven Rostedt
2017-09-06 20:58 ` Patel, Vedang
2017-09-05 21:57 ` [PATCH v2 03/40] tracing: Remove code which merges duplicates Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 04/40] tracing: Add hist_field_name() accessor Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 05/40] tracing: Reimplement log2 Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 06/40] ring-buffer: Add interface for setting absolute time stamps Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 07/40] tracing: Apply absolute timestamps to instance max buffer Tom Zanussi
2017-09-06 19:57 ` Steven Rostedt
2017-09-07 0:49 ` Steven Rostedt
2017-09-07 1:15 ` Liu, Baohong
2017-09-05 21:57 ` [PATCH v2 08/40] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP Tom Zanussi
2017-09-07 14:35 ` Steven Rostedt
2017-09-07 15:05 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 09/40] tracing: Give event triggers access to ring_buffer_event Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 10/40] tracing: Add ring buffer event param to hist field functions Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 11/40] tracing: Increase tracing map KEYS_MAX size Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 12/40] tracing: Break out hist trigger assignment parsing Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 13/40] tracing: Make traceprobe parsing code reusable Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 14/40] tracing: Add hist trigger timestamp support Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 15/40] tracing: Add per-element variable support to tracing_map Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 16/40] tracing: Add hist_data member to hist_field Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 17/40] tracing: Add usecs modifier for hist trigger timestamps Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 18/40] tracing: Add variable support to hist triggers Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 19/40] tracing: Account for variables in named trigger compatibility Tom Zanussi
2017-09-07 16:40 ` Steven Rostedt
2017-09-07 17:00 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 20/40] tracing: Add simple expression support to hist triggers Tom Zanussi
2017-09-07 16:46 ` Steven Rostedt
2017-09-07 17:01 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 21/40] tracing: Generalize per-element hist trigger data Tom Zanussi
2017-09-07 17:56 ` Steven Rostedt
2017-09-07 18:14 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 22/40] tracing: Pass tracing_map_elt to hist_field accessor functions Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 23/40] tracing: Add hist_field 'type' field Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 24/40] tracing: Add variable reference handling to hist triggers Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 25/40] tracing: Add support for dynamic tracepoints Tom Zanussi
2017-09-05 23:29 ` Mathieu Desnoyers
2017-09-06 2:35 ` Tom Zanussi
2017-09-07 22:02 ` Steven Rostedt
2017-09-08 14:18 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 26/40] tracing: Add hist trigger action hook Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 27/40] tracing: Add support for 'synthetic' events Tom Zanussi
2017-09-07 23:40 ` Steven Rostedt
2017-09-08 14:30 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 28/40] tracing: Add support for 'field variables' Tom Zanussi
2017-09-07 23:43 ` Steven Rostedt
2017-09-08 15:37 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 29/40] tracing: Add 'onmatch' hist trigger action support Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 30/40] tracing: Add 'onmax' " Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 31/40] tracing: Allow whitespace to surround hist trigger filter Tom Zanussi
2017-09-08 18:50 ` Steven Rostedt
2017-09-08 19:08 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 32/40] tracing: Add cpu field for hist triggers Tom Zanussi
2017-09-08 19:08 ` Steven Rostedt
2017-09-08 19:35 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 33/40] tracing: Add hist trigger support for variable reference aliases Tom Zanussi
2017-09-08 19:09 ` Steven Rostedt
2017-09-08 19:41 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 34/40] tracing: Add 'last error' error facility for hist triggers Tom Zanussi
2017-09-08 19:25 ` Steven Rostedt
2017-09-08 19:44 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 35/40] tracing: Reverse the order event_mutex/trace_types_lock are taken Tom Zanussi
2017-09-08 19:31 ` Steven Rostedt
2017-09-08 19:41 ` Steven Rostedt [this message]
2017-09-08 20:00 ` Steven Rostedt
2017-09-05 21:57 ` [PATCH v2 36/40] tracing: Remove lookups from tracing_map hitcount Tom Zanussi
2017-09-12 2:16 ` Masami Hiramatsu
2017-09-12 14:16 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 37/40] tracing: Add inter-event hist trigger Documentation Tom Zanussi
2017-09-20 14:44 ` Julia Cartwright
2017-09-20 17:15 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 38/40] tracing: Make tracing_set_clock() non-static Tom Zanussi
2017-09-12 2:18 ` Masami Hiramatsu
2017-09-12 14:18 ` Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 39/40] tracing: Add a clock attribute for hist triggers Tom Zanussi
2017-09-05 21:57 ` [PATCH v2 40/40] tracing: Add trace_event_buffer_reserve() variant that allows recursion Tom Zanussi
2017-09-07 22:29 ` kbuild test robot
2017-09-07 22:35 ` kbuild test robot
2017-09-08 20:27 ` Steven Rostedt
2017-09-08 20:41 ` Tom Zanussi
2017-09-12 1:50 ` [PATCH v2 00/40] tracing: Inter-event (e.g. latency) support Masami Hiramatsu
2017-09-12 14:14 ` Tom Zanussi
2017-09-19 16:31 ` Steven Rostedt
2017-09-19 18:44 ` Tom Zanussi
2017-09-21 20:20 ` Steven Rostedt
2017-09-21 21:11 ` Tom Zanussi
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