Messages in this thread Patch in this message | | | Date | Thu, 20 Aug 2020 15:59:23 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 0/9] TRACE_IRQFLAGS wreckage |
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On Thu, 20 Aug 2020 19:20:46 +0200 Marco Elver <elver@google.com> wrote:
> On Thu, Aug 20, 2020 at 04:58PM +0200, peterz@infradead.org wrote: > > On Thu, Aug 20, 2020 at 10:36:43AM -0400, Steven Rostedt wrote: > > > > > > I tested this series on top of tip/master and triggered the below > > > warning when running the irqsoff tracer boot up test (config attached). > > > > > > -- Steve > > > > > > Testing tracer irqsoff: > > > > > > ============================= > > > WARNING: suspicious RCU usage > > > 5.9.0-rc1-test+ #92 Not tainted > > > ----------------------------- > > > include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage! > ... > > > > Shiny, I think that wants something like the below, but let me go frob > > my config and test it. > > > > --- > > --- a/drivers/cpuidle/cpuidle.c > > +++ b/drivers/cpuidle/cpuidle.c > ... > > With that applied (manually, due to conflicts), I still get warnings for > certain call locations with KCSAN on (that is with my fix from the other > email): > > | ============================= > | WARNING: suspicious RCU usage > | 5.9.0-rc1+ #23 Tainted: G W > | ----------------------------- > | include/trace/events/random.h:310 suspicious rcu_dereference_check() usage! > | > | other info that might help us debug this: > | > | > | rcu_scheduler_active = 2, debug_locks = 0 > | RCU used illegally from extended quiescent state! > | no locks held by swapper/1/0. > | > | stack backtrace: > | CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.9.0-rc1+ #23 > | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 > | Call Trace: > | __dump_stack lib/dump_stack.c:77 [inline] > | dump_stack+0xf1/0x14d lib/dump_stack.c:118 > | trace_prandom_u32 include/trace/events/random.h:310 [inline] > | prandom_u32+0x1ee/0x200 lib/random32.c:86 > | prandom_u32_max include/linux/prandom.h:46 [inline] > | reset_kcsan_skip kernel/kcsan/core.c:277 [inline] > | kcsan_setup_watchpoint+0x9b/0x600 kernel/kcsan/core.c:424 > | is_idle_task+0xd/0x20 include/linux/sched.h:1671 <==== inline, but not noinstr > | irqentry_enter+0x17/0x50 kernel/entry/common.c:293 <==== noinstr function >
What happens if you apply the below patch?
-- Steve
diff --git a/lib/random32.c b/lib/random32.c index 932345323af0..1c5607a411d4 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -83,7 +83,7 @@ u32 prandom_u32(void) u32 res; res = prandom_u32_state(state); - trace_prandom_u32(res); + trace_prandom_u32_rcuidle(res); put_cpu_var(net_rand_state); return res;
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