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linux/kernel/trace
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Steven Rostedt (Red Hat) 561a4fe851 tracing: Use rcu_dereference_sched() for trace event triggers 
As trace event triggers are now part of the mainline kernel, I added
my trace event trigger tests to my test suite I run on all my kernels.
Now these tests get run under different config options, and one of
those options is CONFIG_PROVE_RCU, which checks under lockdep that
the rcu locking primitives are being used correctly. This triggered
the following splat:

===============================
[ INFO: suspicious RCU usage. ]
3.15.0-rc2-test+ #11 Not tainted
-------------------------------
kernel/trace/trace_events_trigger.c:80 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
4 locks held by swapper/1/0:
 #0:  ((&(&j_cdbs->work)->timer)){..-...}, at: [<ffffffff8104d2cc>] call_timer_fn+0x5/0x1be
 #1:  (&(&pool->lock)->rlock){-.-...}, at: [<ffffffff81059856>] __queue_work+0x140/0x283
 #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff8106e961>] try_to_wake_up+0x2e/0x1e8
 #3:  (&rq->lock){-.-.-.}, at: [<ffffffff8106ead3>] try_to_wake_up+0x1a0/0x1e8

stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.15.0-rc2-test+ #11
Hardware name:                  /DG965MQ, BIOS MQ96510J.86A.0372.2006.0605.1717 06/05/2006
 0000000000000001 ffff88007e083b98 ffffffff819f53a5 0000000000000006
 ffff88007b0942c0 ffff88007e083bc8 ffffffff81081307 ffff88007ad96d20
 0000000000000000 ffff88007af2d840 ffff88007b2e701c ffff88007e083c18
Call Trace:
 <IRQ>  [<ffffffff819f53a5>] dump_stack+0x4f/0x7c
 [<ffffffff81081307>] lockdep_rcu_suspicious+0x107/0x110
 [<ffffffff810ee51c>] event_triggers_call+0x99/0x108
 [<ffffffff810e8174>] ftrace_event_buffer_commit+0x42/0xa4
 [<ffffffff8106aadc>] ftrace_raw_event_sched_wakeup_template+0x71/0x7c
 [<ffffffff8106bcbf>] ttwu_do_wakeup+0x7f/0xff
 [<ffffffff8106bd9b>] ttwu_do_activate.constprop.126+0x5c/0x61
 [<ffffffff8106eadf>] try_to_wake_up+0x1ac/0x1e8
 [<ffffffff8106eb77>] wake_up_process+0x36/0x3b
 [<ffffffff810575cc>] wake_up_worker+0x24/0x26
 [<ffffffff810578bc>] insert_work+0x5c/0x65
 [<ffffffff81059982>] __queue_work+0x26c/0x283
 [<ffffffff81059999>] ? __queue_work+0x283/0x283
 [<ffffffff810599b7>] delayed_work_timer_fn+0x1e/0x20
 [<ffffffff8104d3a6>] call_timer_fn+0xdf/0x1be^M
 [<ffffffff8104d2cc>] ? call_timer_fn+0x5/0x1be
 [<ffffffff81059999>] ? __queue_work+0x283/0x283
 [<ffffffff8104d823>] run_timer_softirq+0x1a4/0x22f^M
 [<ffffffff8104696d>] __do_softirq+0x17b/0x31b^M
 [<ffffffff81046d03>] irq_exit+0x42/0x97
 [<ffffffff81a08db6>] smp_apic_timer_interrupt+0x37/0x44
 [<ffffffff81a07a2f>] apic_timer_interrupt+0x6f/0x80
 <EOI>  [<ffffffff8100a5d8>] ? default_idle+0x21/0x32
 [<ffffffff8100a5d6>] ? default_idle+0x1f/0x32
 [<ffffffff8100ac10>] arch_cpu_idle+0xf/0x11
 [<ffffffff8107b3a4>] cpu_startup_entry+0x1a3/0x213
 [<ffffffff8102a23c>] start_secondary+0x212/0x219

The cause is that the triggers are protected by rcu_read_lock_sched() but
the data is dereferenced with rcu_dereference() which expects it to
be protected with rcu_read_lock(). The proper reference should be
rcu_dereference_sched().

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-05-02 23:12:42 -04:00
..
blktrace.c Most of the changes were largely clean ups, and some documentation. 2014-04-03 10:26:31 -07:00
ftrace.c ftrace/module: Hardcode ftrace_module_init() call into load_module() 2014-04-28 10:37:21 -04:00
Kconfig uprobes: Kconfig dependency fix 2014-03-18 16:39:33 -04:00
Makefile tracing: Add basic event trigger framework 2013-12-20 18:40:22 -05:00
power-traces.c PM / tracing: remove deprecated power trace API 2013-01-26 00:39:12 +01:00
ring_buffer_benchmark.c trace: Replace hardcoding of 19 with MAX_NICE 2014-02-27 12:41:03 +01:00
ring_buffer.c trace, ring-buffer: Fix CPU hotplug callback registration 2014-03-20 13:43:48 +01:00
rpm-traces.c
trace_branch.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_clock.c tracing: Add "uptime" trace clock that uses jiffies 2013-03-15 00:36:09 -04:00
trace_entries.h tracing: Add trace_puts() for even faster trace_printk() tracing 2013-03-15 00:35:55 -04:00
trace_event_perf.c perf: Disallow user-space stack dumps for function trace events 2014-03-11 11:57:58 +01:00
trace_events_filter_test.h
trace_events_filter.c tracing: Add and use generic set_trigger_filter() implementation 2013-12-21 22:02:17 -05:00
trace_events_trigger.c tracing: Use rcu_dereference_sched() for trace event triggers 2014-05-02 23:12:42 -04:00
trace_events.c tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints 2014-04-08 20:43:28 -04:00
trace_export.c tracing: Fix anonymous unions in struct ftrace_event_call 2014-04-09 20:02:55 -04:00
trace_functions_graph.c tracing: Pass trace_array to set_flag callback 2014-02-20 12:13:07 -05:00
trace_functions.c tracing: Do not try to recreated toplevel set_ftrace_* files 2014-04-16 19:21:53 -04:00
trace_irqsoff.c Most of the changes were largely clean ups, and some documentation. 2014-04-03 10:26:31 -07:00
trace_kdb.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_kprobe.c tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints 2014-04-08 20:43:28 -04:00
trace_mmiotrace.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_nop.c tracing: Set up infrastructure to allow tracers for instances 2014-02-20 12:13:10 -05:00
trace_output.c tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints 2014-04-08 20:43:28 -04:00
trace_output.h tracing: Rename trace_event_mutex to trace_event_sem 2013-03-15 13:22:10 -04:00
trace_printk.c tracing: Add __tracepoint_string() to export string pointers 2013-07-26 13:39:44 -04:00
trace_probe.c tracing/uprobes: Add @+file_offset fetch method 2014-01-02 20:57:05 -05:00
trace_probe.h tracing/uprobes: Support ftrace_event_file base multibuffer 2014-02-20 12:30:09 -05:00
trace_sched_switch.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_sched_wakeup.c tracing: Pass trace_array to flag_changed callback 2014-02-20 12:13:08 -05:00
trace_selftest_dynamic.c
trace_selftest.c sched/deadline: Add latency tracing for SCHED_DEADLINE tasks 2014-01-13 13:41:11 +01:00
trace_stack.c tracing: Add BUG_ON when stack end location is over written 2014-03-24 10:39:11 -04:00
trace_stat.c trace/trace_stat: use rbtree postorder iteration helper instead of opencoding 2013-11-05 16:01:47 -05:00
trace_stat.h
trace_syscalls.c tracing: Consolidate event trigger code 2014-01-09 21:20:07 -05:00
trace_uprobe.c tracing/uprobes: Fix uprobe_cpu_buffer memory leak 2014-04-17 10:44:42 -04:00
trace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
trace.h kernel: use macros from compiler.h instead of __attribute__((...)) 2014-04-07 16:36:11 -07:00