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From: Marc Zyngier <maz@kernel.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Mel Gorman <mgorman@techsingularity.net>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [SPLAT 2/3] irqchip/gic-v3-its: Sleeping spinlocks down gic_reserve_range()
Date: Wed, 11 Aug 2021 09:50:02 +0100	[thread overview]
Message-ID: <87y2989xhh.wl-maz@kernel.org> (raw)
In-Reply-To: <20210810134127.1394269-3-valentin.schneider@arm.com>

[+ Ard]

On Tue, 10 Aug 2021 14:41:26 +0100,
Valentin Schneider <valentin.schneider@arm.com> wrote:
> 
> [    0.134518] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:35
> [    0.134520] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/1
> [    0.134522] 1 lock held by swapper/1/0:
> [    0.134523] #0: ffff008f3624f728 ((lock).lock){+.+.}-{2:2}, at: get_page_from_freelist (mm/page_alloc.c:3673 mm/page_alloc.c:3704 mm/page_alloc.c:4166) 
> [    0.134533] irq event stamp: 0
> [    0.134534] hardirqs last enabled at (0): 0x0 
> [    0.134538] hardirqs last disabled at (0): copy_process (./include/linux/lockdep.h:195 ./include/linux/lockdep.h:202 ./include/linux/lockdep.h:208 ./include/linux/seqlock.h:78 kernel/fork.c:2084) 
> [    0.134542] softirqs last enabled at (0): copy_process (./include/linux/lockdep.h:195 ./include/linux/lockdep.h:202 ./include/linux/lockdep.h:208 ./include/linux/seqlock.h:78 kernel/fork.c:2084) 
> [    0.134545] softirqs last disabled at (0): 0x0 
> [    0.134547] Preemption disabled at:
> [    0.134547] rt_mutex_slowunlock (kernel/locking/rtmutex.c:1223) 
> [    0.134552] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.14.0-rc4-rt6-torture+ #56
> [    0.134555] Call trace:
> [    0.134556] dump_backtrace (arch/arm64/kernel/stacktrace.c:151) 
> [    0.134558] show_stack (arch/arm64/kernel/stacktrace.c:217) 
> [    0.134559] dump_stack_lvl (lib/dump_stack.c:106) 
> [    0.134563] dump_stack (lib/dump_stack.c:113) 
> [    0.134565] ___might_sleep (kernel/sched/core.c:9306) 
> [    0.134567] rt_spin_lock (kernel/locking/rtmutex.c:1641 (discriminator 4) kernel/locking/spinlock_rt.c:30 (discriminator 4) kernel/locking/spinlock_rt.c:36 (discriminator 4) kernel/locking/spinlock_rt.c:44 (discriminator 4)) 
> [    0.134569] get_page_from_freelist (mm/page_alloc.c:3673 mm/page_alloc.c:3704 mm/page_alloc.c:4166) 
> [    0.134571] __alloc_pages (mm/page_alloc.c:5391) 
> [    0.134573] alloc_page_interleave (mm/mempolicy.c:2119) 
> [    0.134576] alloc_pages (mm/mempolicy.c:2249) 
> [    0.134577] new_slab (mm/slub.c:1740 mm/slub.c:1877 mm/slub.c:1940) 
> [    0.134580] ___slab_alloc (mm/slub.c:2951) 
> [    0.134582] __slab_alloc.isra.0 (mm/slub.c:3038) 
> [    0.134584] kmem_cache_alloc_trace (mm/slub.c:3129 mm/slub.c:3171 mm/slub.c:3188) 
> [    0.134587] efi_mem_reserve_iomem (drivers/firmware/efi/efi.c:905) 
> [    0.134590] efi_mem_reserve_persistent (drivers/firmware/efi/efi.c:952) 
> [    0.134593] its_cpu_init (drivers/irqchip/irq-gic-v3-its.c:3074 drivers/irqchip/irq-gic-v3-its.c:5196) 
> [    0.134596] gic_starting_cpu (drivers/irqchip/irq-gic.c:798) 
> [    0.134599] cpuhp_invoke_callback (kernel/cpu.c:180) 
> [    0.134601] cpuhp_invoke_callback_range (kernel/cpu.c:656) 
> [    0.134603] notify_cpu_starting (kernel/cpu.c:1270) 
> [    0.134605] secondary_start_kernel (arch/arm64/kernel/smp.c:243) 
> [    0.134608] __secondary_switched (arch/arm64/kernel/head.S:661) 

The issue is that although the redistributor tables have been
allocated ahead of time (outside of any cpuhp callback), they cannot
be programmed into the RDs until the corresponding CPUs have been
brought up (the registers may not be accessible).

For the same reason, we don't know whether we can free them (because
there is already a table programmed there) or have to reserve them
with an efi_mem_reserve_persistent() call. efi_mem_reserve_iomem()
uses GFP_ATOMIC for its allocation, but this is not sufficient for RT
anymore.

We could postpone the reservation of the memory to a later point (it
is only useful for kexec), but it isn't clear where that point is. The
CPU is not quite up yet, and we can't easily IPI the boot CPU to do
the reserve call.

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-08-11  8:50 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-10 13:41 [SPLAT 0/3] Sleeping spinlocks in troublesome contexts on v5.14-rc4-rt6 Valentin Schneider
2021-08-10 13:41 ` [SPLAT 1/3] arm_pmu: Sleeping spinlocks down armpmu_alloc_atomic() Valentin Schneider
2021-08-10 13:54   ` Sebastian Andrzej Siewior
2021-08-10 17:16     ` Thomas Gleixner
2021-08-10 18:39       ` Sebastian Andrzej Siewior
2021-08-10 19:56         ` Thomas Gleixner
2021-08-10 13:41 ` [SPLAT 2/3] irqchip/gic-v3-its: Sleeping spinlocks down gic_reserve_range() Valentin Schneider
2021-08-11  8:50   ` Marc Zyngier [this message]
2021-08-11 12:28     ` Thomas Gleixner
2021-08-11 15:14       ` Marc Zyngier
2021-08-17 15:16     ` Ard Biesheuvel
2021-08-10 13:41 ` [SPLAT 3/3] gpio: dwapb: Sleeping spinlocks down IRQ mapping Valentin Schneider
2021-08-10 20:33   ` Thomas Gleixner
2021-08-11 10:52   ` Andy Shevchenko

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