From: Tom Zanussi <zanussi@kernel.org> To: Steven Rostedt <rostedt@goodmis.org>, Rasmus Villemoes <rasmus.villemoes@prevas.dk> Cc: linux-kernel@vger.kernel.org, linux-rt-users <linux-rt-users@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Carsten Emde <C.Emde@osadl.org>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, John Kacur <jkacur@redhat.com>, Julia Cartwright <julia@ni.com>, Daniel Wagner <wagi@monom.org>, Julien Grall <julien.grall@arm.com> Subject: Re: [PATCH RT 10/30] hrtimer: Prevent using hrtimer_grab_expiry_lock() on migration_base Date: Mon, 27 Apr 2020 14:26:52 -0500 Message-ID: <2535a046bc15f28478c5289742e617a468becbd6.camel@kernel.org> (raw) In-Reply-To: <20200427150626.4f217c82@gandalf.local.home> On Mon, 2020-04-27 at 15:06 -0400, Steven Rostedt wrote: > On Mon, 27 Apr 2020 15:10:00 +0200 > Rasmus Villemoes <rasmus.villemoes@prevas.dk> wrote: > > > However, building with their rescue initrd and booting that, the > > board > > would consistently hang during reboot. Sometimes I would get lines > > like > > > > [ 72.956630] sched: RT throttling activated > > [ 72.973769] lanx: port 1(lan1) entered disabled state > > [ 73.000401] lanx: port 2(lan2) entered disabled state > > [ 73.974951] lanx: port 3(lan3) entered disabled state > > [ 73.997473] lanx: port 4(lan4) entered disabled state > > [ 74.968006] lanx: port 5(lan5) entered disabled state > > > > other times there would be no output, but the board was still > > hanging. > > Reverting > > > > b1a471ec4df1 - hrtimer: Prevent using hrtimer_grab_expiry_lock() on > > migration_base > > 40aae5708e7a - hrtimer: Add a missing bracket and hide > > `migration_base' > > on !SMP > > > > on top of v4.19.94-rt39 makes that problem go away, i.e. the board > > reboots as expected. > > > > The board is a 32 bit powerpc (mpc8309) !SMP. Any ideas what I can > > do to > > debug this further? > > Thanks Rasmus for looking into this. Tom now maintains 4.19-rt. > > Tom, care to pull in these patches on top of 4.19-rt? > Those patches are already in 4.19-rt - he's saying that reverting them fixes the problem. I'm guessing that the assumption of base or base->cpu_base always being non-NULL in those patches might be wrong. If so, the below patch should fix the problem: Subject: [PATCH] hrtimer: Add back base and base->cpu_base checks in hrtimer_grab_expiry_lock() 4.19 commit b1a471ec4df1 [hrtimer: Prevent using hrtimer_grab_expiry_lock() on migration_base] removed the NULL checks for timer->base and timer->base->cpu_base on the assumption that they're always non-NULL. That assumption is apparently not to be true, so add the checks back. Signed-off-by: Tom Zanussi <zanussi@kernel.org> --- kernel/time/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index e54a95de8b79..6f20cf23008b 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -953,7 +953,7 @@ void hrtimer_grab_expiry_lock(const struct hrtimer *timer) { struct hrtimer_clock_base *base = READ_ONCE(timer->base); - if (timer->is_soft && is_migration_base(base)) { + if (timer->is_soft && base && base->cpu_base && is_migration_base(base)) { spin_lock(&base->cpu_base->softirq_expiry_lock); spin_unlock(&base->cpu_base->softirq_expiry_lock); } -- 2.17.1 > -- Steve
next prev parent reply index Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-23 20:39 [PATCH RT 00/30] Linux 4.19.94-rt39-rc2 Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 01/30] i2c: exynos5: Remove IRQF_ONESHOT Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 02/30] i2c: hix5hd2: " Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 03/30] sched/deadline: Ensure inactive_timer runs in hardirq context Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 04/30] thermal/x86_pkg_temp: make pkg_temp_lock a raw spinlock Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 05/30] dma-buf: Use seqlock_t instread disabling preemption Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 06/30] KVM: arm/arm64: Let the timer expire in hardirq context on RT Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 07/30] x86: preempt: Check preemption level before looking at lazy-preempt Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 08/30] hrtimer: Use READ_ONCE to access timer->base in hrimer_grab_expiry_lock() Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 09/30] hrtimer: Dont grab the expiry lock for non-soft hrtimer Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 10/30] hrtimer: Prevent using hrtimer_grab_expiry_lock() on migration_base Steven Rostedt 2020-04-27 13:10 ` Rasmus Villemoes 2020-04-27 19:06 ` Steven Rostedt 2020-04-27 19:26 ` Tom Zanussi [this message] 2020-04-28 6:51 ` Rasmus Villemoes 2020-04-28 7:03 ` Rasmus Villemoes 2020-04-28 12:59 ` Tom Zanussi 2020-04-28 13:07 ` Rasmus Villemoes 2020-04-28 13:43 ` Tom Zanussi 2020-01-23 20:39 ` [PATCH RT 11/30] hrtimer: Add a missing bracket and hide `migration_base on !SMP Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 12/30] posix-timers: Unlock expiry lock in the early return Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 14/30] sched: __set_cpus_allowed_ptr: Check cpus_mask, not cpus_ptr Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 15/30] sched: Remove dead __migrate_disabled() check Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 16/30] sched: migrate disable: Protect cpus_ptr with lock Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 17/30] lib/smp_processor_id: Dont use cpumask_equal() Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 18/30] futex: Make the futex_hash_bucket spinlock_t again and bring back its old state Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 19/30] locking/rtmutex: Clean ->pi_blocked_on in the error case Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 20/30] lib/ubsan: Dont seralize UBSAN report Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 21/30] kmemleak: Change the lock of kmemleak_object to raw_spinlock_t Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 22/30] sched: migrate_enable: Use select_fallback_rq() Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 23/30] sched: Lazy migrate_disable processing Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 24/30] sched: migrate_enable: Use stop_one_cpu_nowait() Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 25/30] Revert "ARM: Initialize split page table locks for vector page" Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 26/30] locking: Make spinlock_t and rwlock_t a RCU section on RT Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 27/30] sched/core: migrate_enable() must access takedown_cpu_task on !HOTPLUG_CPU Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 28/30] lib/smp_processor_id: Adjust check_preemption_disabled() Steven Rostedt 2020-01-23 20:39 ` [PATCH RT 29/30] sched: migrate_enable: Busy loop until the migration request is completed Steven Rostedt 2020-01-23 20:40 ` [PATCH RT 30/30] Linux 4.19.94-rt39-rc2 Steven Rostedt
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