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
ftrace.c
Kconfig
Makefile
power-traces.c
ring_buffer_benchmark.c
ring_buffer.c
rpm-traces.c
trace_branch.c
trace_clock.c
trace_entries.h
trace_event_perf.c
trace_events_filter_test.h
trace_events_filter.c
trace_events_trigger.c	tracing: Use rcu_dereference_sched() for trace event triggers	2014-05-02 23:12:42 -04:00
trace_events.c
trace_export.c
trace_functions_graph.c
trace_functions.c
trace_irqsoff.c
trace_kdb.c
trace_kprobe.c
trace_mmiotrace.c
trace_nop.c
trace_output.c
trace_output.h
trace_printk.c
trace_probe.c
trace_probe.h
trace_sched_switch.c
trace_sched_wakeup.c
trace_selftest_dynamic.c
trace_selftest.c
trace_stack.c
trace_stat.c
trace_stat.h
trace_syscalls.c
trace_uprobe.c
trace.c
trace.h