Messages in this thread | | | Date | Sat, 1 Sep 2018 21:16:39 -0700 | From | "Paul E. McKenney" <> | Subject | Re: 4.19-rc1: ./include/linux/rcupdate.h:631 rcu_read_lock() used illegally while idle! |
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On Sat, Sep 01, 2018 at 06:45:31PM -0400, Steven Rostedt wrote: > On Sat, 1 Sep 2018 10:54:42 -0700 > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > > > On Sat, Sep 01, 2018 at 07:35:59PM +0200, Borislav Petkov wrote: > > > This is a huge splat! It haz some perf* and sched* in it, I guess for > > > peterz to stare at. And lemme add Paul for good measure too :) > > > > > > Kernel is -rc1 + 3 microcode loader patches ontop which should not be > > > related. > > > > It really is tracing from the idle loop. But I thought that the event > > tracing took care of that. Adding Steve and Joel for their thoughts. > > > > Thanx, Paul > > > > > Thx. > > > > > > --- > > > [ 62.409125] ============================= > > > [ 62.409129] WARNING: suspicious RCU usage > > > [ 62.409133] 4.19.0-rc1+ #1 Not tainted > > > [ 62.409136] ----------------------------- > > > [ 62.409140] ./include/linux/rcupdate.h:631 rcu_read_lock() used illegally while idle! > > > [ 62.409143] > > > other info that might help us debug this: > > > > > > [ 62.409147] > > > RCU used illegally from idle CPU! > > > rcu_scheduler_active = 2, debug_locks = 1 > > > [ 62.409151] RCU used illegally from extended quiescent state! > > > [ 62.409155] 1 lock held by swapper/0/0: > > > [ 62.409158] #0: 000000004557ee0e (rcu_read_lock){....}, at: perf_event_output_forward+0x0/0x130 > > > [ 62.409175] > > > stack backtrace: > > > [ 62.409180] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0-rc1+ #1 > > > [ 62.409183] Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012 > > > [ 62.409187] Call Trace: > > > [ 62.409196] dump_stack+0x85/0xcb > > > [ 62.409203] perf_event_output_forward+0xf6/0x130 > > I think this is because we switched the trace point code to be > protected by srcu instead of rcu_lock_sched() and a song and dance to > "make RCU watch again" if it is not, but perf is using normal > rcu_read_lock() internally even though it is hooked into the > tracepoint code. Should perf switch to SRCU, or perhaps it can do the > song and dance to make RCU watch again?
Well, this is a regression, so in theory we could push my three SRCU patches into the current merge window, which would allow perf going to SRCU, thus fixing the above splat. I am OK either way. What would you prefer?
Thanx, Paul
> -- Steve > > > > > [ 62.409215] __perf_event_overflow+0x52/0xe0 > > > [ 62.409223] perf_swevent_overflow+0x91/0xb0 > > > [ 62.409229] perf_tp_event+0x11a/0x350 > > > [ 62.409235] ? find_held_lock+0x2d/0x90 > > > [ 62.409251] ? __lock_acquire+0x2ce/0x1350 > > > [ 62.409263] ? __lock_acquire+0x2ce/0x1350 > > > [ 62.409270] ? retint_kernel+0x2d/0x2d > > > [ 62.409278] ? find_held_lock+0x2d/0x90 > > > [ 62.409285] ? tick_nohz_get_sleep_length+0x83/0xb0 > > > [ 62.409299] ? perf_trace_cpu+0xbb/0xd0 > > > [ 62.409306] ? perf_trace_buf_alloc+0x5a/0xa0 > > > [ 62.409311] perf_trace_cpu+0xbb/0xd0 > > > [ 62.409323] cpuidle_enter_state+0x185/0x340 > > > [ 62.409332] do_idle+0x1eb/0x260 > > > [ 62.409340] cpu_startup_entry+0x5f/0x70 > > > [ 62.409347] start_kernel+0x49b/0x4a6 > > > > > > [ 62.409357] secondary_startup_64+0xa4/0xb0 >
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