On Wed, Sep 05, 2018 at 09:26:29AM -0400, Steven Rostedt wrote: > On Wed, 5 Sep 2018 05:59:41 -0700 > "Paul E. McKenney" <[email protected]> wrote: > > > On Wed, Sep 05, 2018 at 10:22:54AM +0200, Borislav Petkov wrote: > > > On Tue, Sep 04, 2018 at 01:53:21PM -0700, Paul E. McKenney wrote: > > > > I must defer to Borislav on this one. Assuming it has the desired > > > > effect, I am good with it. > > > > > > It did survive a bunch of reboots (the WARN would fire after boot > > > finishes, normally) so I guess we can run with it and see how it works > > > out in the next couple of weeks. > > > > > > Thanks guys! > > > > Woo-hoo!!! Thank you for testing this! > > > > Here's the official patch if you want to add an Ack/review/tested-by: > > -- Steve > > From: "Steven Rostedt (VMware)" <[email protected]> > > Borislav reported the following splat: > > ============================= > WARNING: suspicious RCU usage > 4.19.0-rc1+ #1 Not tainted > ----------------------------- > ./include/linux/rcupdate.h:631 rcu_read_lock() used illegally while idle! > other info that might help us debug this: > > RCU used illegally from idle CPU! > rcu_scheduler_active = 2, debug_locks = 1 > RCU used illegally from extended quiescent state! > 1 lock held by swapper/0/0: > #0: 000000004557ee0e (rcu_read_lock){....}, at: > perf_event_output_forward+0x0/0x130 > > stack backtrace: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0-rc1+ #1 > Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012 > Call Trace: > dump_stack+0x85/0xcb > perf_event_output_forward+0xf6/0x130 > __perf_event_overflow+0x52/0xe0 > perf_swevent_overflow+0x91/0xb0 > perf_tp_event+0x11a/0x350 > ? find_held_lock+0x2d/0x90 > ? __lock_acquire+0x2ce/0x1350 > ? __lock_acquire+0x2ce/0x1350 > ? retint_kernel+0x2d/0x2d > ? find_held_lock+0x2d/0x90 > ? tick_nohz_get_sleep_length+0x83/0xb0 > ? perf_trace_cpu+0xbb/0xd0 > ? perf_trace_buf_alloc+0x5a/0xa0 > perf_trace_cpu+0xbb/0xd0 > cpuidle_enter_state+0x185/0x340 > do_idle+0x1eb/0x260 > cpu_startup_entry+0x5f/0x70 > start_kernel+0x49b/0x4a6 > secondary_startup_64+0xa4/0xb0 > > This is due to the tracepoints moving to SRCU usage which does not require > RCU to be "watching". But perf uses these tracepoints with RCU and expects > it to be. Hence, we still need to add in the rcu_irq_enter/exit_irqson() > calls for "rcuidle" tracepoints. This is a temporary fix until we have SRCU > working in NMI context, and then perf can be converted to use that instead > of normal RCU. > > Link: http://lkml.kernel.org/r/[email protected] > > Cc: x86-ml <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > Reported-by: Borislav Petkov <[email protected]> > Fixes: e6753f23d961d ("tracepoint: Make rcuidle tracepoint callers use SRCU") > Signed-off-by: Steven Rostedt (VMware) <[email protected]>
Reviewed-by: "Paul E. McKenney" <[email protected]> > --- > include/linux/tracepoint.h | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 7f2e16e76ac4..041f7e56a289 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -158,8 +158,10 @@ extern void syscall_unregfunc(void); > * For rcuidle callers, use srcu since sched-rcu \ > * doesn't work from the idle path. \ > */ \ > - if (rcuidle) \ > + if (rcuidle) { \ > idx = srcu_read_lock_notrace(&tracepoint_srcu); \ > + rcu_irq_enter_irqson(); \ > + } \ > \ > it_func_ptr = rcu_dereference_raw((tp)->funcs); \ > \ > @@ -171,8 +173,10 @@ extern void syscall_unregfunc(void); > } while ((++it_func_ptr)->func); \ > } \ > \ > - if (rcuidle) \ > + if (rcuidle) { \ > + rcu_irq_exit_irqson(); \ > srcu_read_unlock_notrace(&tracepoint_srcu, idx);\ > + } \ > \ > preempt_enable_notrace(); \ > } while (0) > -- > 2.13.6 >
