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Message-ID: <CAOJe8K1G3n8Mfi=421og9wOnyq2n-45x69JpQe80-D2xzRE95Q@mail.gmail.com> Date: Tue, 16 Feb 2016 08:52:24 +0300 From: Denis Kirjanov <kda@...ux-powerpc.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com Subject: Re: [PATCH 1/2] tracing/mm: don't trace kfree on offline CPUs On 2/15/16, Steven Rostedt <rostedt@...dmis.org> wrote: > On Sun, 14 Feb 2016 23:19:42 +0300 > Denis Kirjanov <kda@...ux-powerpc.org> wrote: > > >> >> TP_PROTO(unsigned long call_site, const void *ptr), >> >> >> >> - TP_ARGS(call_site, ptr) >> >> + TP_ARGS(call_site, ptr), >> >> + >> >> + /* >> >> + * This trace can be potentially called from an offlined cpu. >> >> + * Since trace points use RCU and RCU should not be used from >> >> + * offline cpus, filter such calls out. >> >> + * While this trace can be called from a preemptable section, >> >> + * it has no impact on the condition since tasks can migrate >> >> + * only from online cpus to other online cpus. Thus its safe >> >> + * to use raw_smp_processor_id. >> >> + */ >> >> + TP_CONDITION(cpu_online(raw_smp_processor_id())) >> > >> > This is starting to become a common occurrence. Perhaps it is best to >> > just hardcode this into the tracepoint code itself? >> >> Can you take it as a fix for now. I'll post the follow-up patch then >> for rcu and offline cpus >> issue. > > Actually, I prefer not to add more checks for cpu_online(), if its > going to become the default. > > Does this work for you instead? Hm, somehow it doesn't work: [ 84.692846] =============================== [ 84.692847] [ INFO: suspicious RCU usage. ] [ 84.692849] 4.5.0-rc3-00765-g78b70d4-dirty #36 Tainted: G S [ 84.692850] ------------------------------- [ 84.692851] include/trace/events/rcu.h:457 suspicious rcu_dereference_check() usage! [ 84.692852] other info that might help us debug this: [ 84.692854] RCU used illegally from offline CPU! rcu_scheduler_active = 1, debug_locks = 1 [ 84.692855] no locks held by swapper/11/0. [ 84.692856] stack backtrace: [ 84.692858] CPU: 11 PID: 0 Comm: swapper/11 Tainted: G S 4.5.0-rc3-00765-g78b70d4-dirty #36 [ 84.692860] Call Trace: [ 84.692868] [c0000005b76d37f0] [c0000000008c57ac] .dump_stack+0xe0/0x14c (unreliable) [ 84.692872] [c0000005b76d3880] [c00000000010d0c8] .lockdep_rcu_suspicious+0x108/0x170 [ 84.692876] [c0000005b76d3910] [c00000000013cab4] .__call_rcu.constprop.60+0x244/0x680 [ 84.692880] [c0000005b76d39e0] [c0000000002c38ec] .put_object+0x5c/0x80 [ 84.692884] [c0000005b76d3a60] [c00000000029e748] .kmem_cache_free+0x318/0x4c0 [ 84.692888] [c0000005b76d3b00] [c0000000000936b4] .__mmdrop+0x54/0x150 [ 84.692891] [c0000005b76d3b90] [c0000000000e46e0] .idle_task_exit+0x120/0x130 [ 84.692895] [c0000005b76d3c20] [c000000000075a14] .pseries_mach_cpu_die+0x64/0x310 [ 84.692899] [c0000005b76d3cd0] [c00000000004401c] .cpu_die+0x3c/0x60 [ 84.692902] [c0000005b76d3d40] [c000000000018998] .arch_cpu_idle_dead+0x28/0x40 [ 84.692906] [c0000005b76d3db0] [c000000000102714] .cpu_startup_entry+0x554/0x580 [ 84.692909] [c0000005b76d3ed0] [c000000000043d68] .start_secondary+0x348/0x390 [ 84.692913] [c0000005b76d3f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14 [ 84.692918] =============================== [ 84.692919] [ INFO: suspicious RCU usage. ] [ 84.692920] 4.5.0-rc3-00765-g78b70d4-dirty #36 Tainted: G S [ 84.692921] ------------------------------- [ 84.692922] include/trace/events/kmem.h:141 suspicious rcu_dereference_check() usage! [ 84.692923] other info that might help us debug this: [ 84.692924] RCU used illegally from offline CPU! rcu_scheduler_active = 1, debug_locks = 1 [ 84.692925] no locks held by swapper/11/0. [ 84.692926] stack backtrace: [ 84.692928] CPU: 11 PID: 0 Comm: swapper/11 Tainted: G S 4.5.0-rc3-00765-g78b70d4-dirty #36 [ 84.692929] Call Trace: [ 84.692933] [c0000005b76d38c0] [c0000000008c57ac] .dump_stack+0xe0/0x14c (unreliable) [ 84.692936] [c0000005b76d3950] [c00000000010d0c8] .lockdep_rcu_suspicious+0x108/0x170 [ 84.692939] [c0000005b76d39e0] [c00000000029f1c0] .kfree+0x380/0x470 [ 84.692942] [c0000005b76d3a80] [c000000000056194] .destroy_context+0x44/0x100 [ 84.692946] [c0000005b76d3b00] [c0000000000936c0] .__mmdrop+0x60/0x150 [ 84.692948] [c0000005b76d3b90] [c0000000000e46e0] .idle_task_exit+0x120/0x130 [ 84.692951] [c0000005b76d3c20] [c000000000075a14] .pseries_mach_cpu_die+0x64/0x310 [ 84.692954] [c0000005b76d3cd0] [c00000000004401c] .cpu_die+0x3c/0x60 [ 84.692957] [c0000005b76d3d40] [c000000000018998] .arch_cpu_idle_dead+0x28/0x40 [ 84.692960] [c0000005b76d3db0] [c000000000102714] .cpu_startup_entry+0x554/0x580 [ 84.692963] [c0000005b76d3ed0] [c000000000043d68] .start_secondary+0x348/0x390 [ 84.692966] [c0000005b76d3f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14 > > -- Steve > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index acd522a91539..acfdbf353a0b 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -14,8 +14,10 @@ > * See the file COPYING for more details. > */ > > +#include <linux/smp.h> > #include <linux/errno.h> > #include <linux/types.h> > +#include <linux/cpumask.h> > #include <linux/rcupdate.h> > #include <linux/tracepoint-defs.h> > > @@ -132,6 +134,9 @@ extern void syscall_unregfunc(void); > void *it_func; \ > void *__data; \ > \ > + if (!cpu_online(raw_smp_processor_id())) \ > + return; \ > + \ > if (!(cond)) \ > return; \ > prercu; \ >
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