Hi, Can you please add sta...@vger.kernel.org to the Cc? Without the patch, we get RCU warnings during bootup. Hence the patch is important for the stable kernels as well.
Regards Preeti U Murthy On 03/23/2015 05:54 PM, tip-bot for Preeti U Murthy wrote: > Commit-ID: a127d2bcf1fbc8c8e0b5cf0dab54f7d3ff50ce47 > Gitweb: http://git.kernel.org/tip/a127d2bcf1fbc8c8e0b5cf0dab54f7d3ff50ce47 > Author: Preeti U Murthy <pre...@linux.vnet.ibm.com> > AuthorDate: Wed, 18 Mar 2015 16:19:27 +0530 > Committer: Ingo Molnar <mi...@kernel.org> > CommitDate: Mon, 23 Mar 2015 10:50:05 +0100 > > timers/tick/broadcast-hrtimer: Fix suspicious RCU usage in idle loop > > The hrtimer mode of broadcast queues hrtimers in the idle entry > path so as to wakeup cpus in deep idle states. The associated > call graph is : > > cpuidle_idle_call() > |____ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, ....)) > |_____tick_broadcast_set_event() > |____clockevents_program_event() > |____bc_set_next() > > The hrtimer_{start/cancel} functions call into tracing which uses RCU. > But it is not legal to call into RCU in cpuidle because it is one of the > quiescent states. Hence protect this region with RCU_NONIDLE which informs > RCU that the cpu is momentarily non-idle. > > As an aside it is helpful to point out that the clock event device that is > programmed here is not a per-cpu clock device; it is a > pseudo clock device, used by the broadcast framework alone. > The per-cpu clock device programming never goes through bc_set_next(). > > Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > Reviewed-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > Cc: linuxppc-...@ozlabs.org > Cc: m...@ellerman.id.au > Cc: t...@linutronix.de > Link: > http://lkml.kernel.org/r/20150318104705.17763.56668.st...@preeti.in.ibm.com > Signed-off-by: Ingo Molnar <mi...@kernel.org> > --- > kernel/time/tick-broadcast-hrtimer.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/kernel/time/tick-broadcast-hrtimer.c > b/kernel/time/tick-broadcast-hrtimer.c > index eb682d5..6aac4be 100644 > --- a/kernel/time/tick-broadcast-hrtimer.c > +++ b/kernel/time/tick-broadcast-hrtimer.c > @@ -49,6 +49,7 @@ static void bc_set_mode(enum clock_event_mode mode, > */ > static int bc_set_next(ktime_t expires, struct clock_event_device *bc) > { > + int bc_moved; > /* > * We try to cancel the timer first. If the callback is on > * flight on some other cpu then we let it handle it. If we > @@ -60,9 +61,15 @@ static int bc_set_next(ktime_t expires, struct > clock_event_device *bc) > * restart the timer because we are in the callback, but we > * can set the expiry time and let the callback return > * HRTIMER_RESTART. > + * > + * Since we are in the idle loop at this point and because > + * hrtimer_{start/cancel} functions call into tracing, > + * calls to these functions must be bound within RCU_NONIDLE. > */ > - if (hrtimer_try_to_cancel(&bctimer) >= 0) { > - hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED); > + RCU_NONIDLE(bc_moved = (hrtimer_try_to_cancel(&bctimer) >= 0) ? > + !hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED) : > + 0); > + if (bc_moved) { > /* Bind the "device" to the cpu */ > bc->bound_on = smp_processor_id(); > } else if (bc->bound_on == smp_processor_id()) { > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
