From a05d59a5673339ef6936d6940cdf68172ce75b9f Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 6 Feb 2015 14:30:50 -0500 Subject: tracing: Add condition check to RCU lockdep checks The trace_tlb_flush() tracepoint can be called when a CPU is going offline. When a CPU is offline, RCU is no longer watching that CPU and since the tracepoint is protected by RCU, it must not be called. To prevent the tlb_flush tracepoint from being called when the CPU is offline, it was converted to a TRACE_EVENT_CONDITION where the condition checks if the CPU is online before calling the tracepoint. Unfortunately, this was not enough to stop lockdep from complaining about it. Even though the RCU protected code of the tracepoint will never be called, the condition is hidden within the tracepoint, and even though the condition prevents RCU code from being called, the lockdep checks are outside the tracepoint (this is to test tracepoints even when they are not enabled). Even though tracepoints should be checked to be RCU safe when they are not enabled, the condition should still be considered when checking RCU. Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@mail.gmail.com Fixes: 3a630178fd5f "tracing: generate RCU warnings even when tracepoints are disabled" Cc: stable@vger.kernel.org # 3.18+ Acked-by: Dave Hansen Reported-by: Sedat Dilek Tested-by: Sedat Dilek Signed-off-by: Steven Rostedt --- include/linux/tracepoint.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index e08e21e5f601..c72851328ca9 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -173,7 +173,7 @@ extern void syscall_unregfunc(void); TP_PROTO(data_proto), \ TP_ARGS(data_args), \ TP_CONDITION(cond),,); \ - if (IS_ENABLED(CONFIG_LOCKDEP)) { \ + if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \ rcu_read_lock_sched_notrace(); \ rcu_dereference_sched(__tracepoint_##name.funcs);\ rcu_read_unlock_sched_notrace(); \ -- cgit v1.2.3 From 6c8465a82a605bc692304bab42703017dcfff013 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 6 Feb 2015 14:18:19 -0500 Subject: x86/tlb/trace: Do not trace on CPU that is offline When taking a CPU down for suspend and resume, a tracepoint may be called when the CPU has been designated offline. As tracepoints require RCU for protection, they must not be called if the current CPU is offline. Unfortunately, trace_tlb_flush() is called in this scenario as was noted by LOCKDEP: ... Disabling non-boot CPUs ... intel_pstate CPU 1 exiting =============================== smpboot: CPU 1 didn't die... [ INFO: suspicious RCU usage. ] 3.19.0-rc7-next-20150204.1-iniza-small #1 Not tainted ------------------------------- include/trace/events/tlb.h:35 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 1, debug_locks = 0 no locks held by swapper/1/0. stack backtrace: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.19.0-rc7-next-20150204.1-iniza-small #1 Hardware name: SAMSUNG ELECTRONICS CO., LTD. 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013 0000000000000001 ffff88011a44fe18 ffffffff817e370d 0000000000000011 ffff88011a448290 ffff88011a44fe48 ffffffff810d6847 ffff8800c66b9600 0000000000000001 ffff88011a44c000 ffffffff81cb3900 ffff88011a44fe78 Call Trace: [] dump_stack+0x4c/0x65 [] lockdep_rcu_suspicious+0xe7/0x120 [] idle_task_exit+0x205/0x2c0 [] play_dead_common+0xe/0x50 [] native_play_dead+0x15/0x140 [] arch_cpu_idle_dead+0xf/0x20 [] cpu_startup_entry+0x37e/0x580 [] start_secondary+0x140/0x150 intel_pstate CPU 2 exiting ... By converting the tlb_flush tracepoint to a TRACE_EVENT_CONDITION where the condition is cpu_online(smp_processor_id()), we can avoid calling RCU protected code when the CPU is offline. Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@mail.gmail.com Cc: stable@vger.kernel.org # 3.17+ Fixes: d17d8f9dedb9 "x86/mm: Add tracepoints for TLB flushes" Reported-by: Sedat Dilek Tested-by: Sedat Dilek Suggested-by: Paul E. McKenney Acked-by: Paul E. McKenney Acked-by: Dave Hansen Signed-off-by: Steven Rostedt --- include/trace/events/tlb.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/trace/events/tlb.h b/include/trace/events/tlb.h index 13391d288107..0e7635765153 100644 --- a/include/trace/events/tlb.h +++ b/include/trace/events/tlb.h @@ -13,11 +13,13 @@ { TLB_LOCAL_SHOOTDOWN, "local shootdown" }, \ { TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" } -TRACE_EVENT(tlb_flush, +TRACE_EVENT_CONDITION(tlb_flush, TP_PROTO(int reason, unsigned long pages), TP_ARGS(reason, pages), + TP_CONDITION(cpu_online(smp_processor_id())), + TP_STRUCT__entry( __field( int, reason) __field(unsigned long, pages) -- cgit v1.2.3