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SubjectRe: [PATCH] perf: arm_pmu_acpi: Fix armpmu_alloc call from invalid context
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On Thu, 2018-02-08 at 17:54 +0000, Mark Rutland wrote:
> Hi Mark,
>
> On Thu, Feb 08, 2018 at 12:45:04PM -0500, Mark Salter wrote:
> > When booting an arm64 debug kernel with ACPI, I see:
> >
> > BUG: sleeping function called from invalid context at mm/slab.h:420
> > in_atomic(): 0, irqs_disabled(): 128, pid: 12, name: cpuhp/0
> > 1 lock held by cpuhp/0/12:
> > #0: (cpuhp_state-up){+.+.}, at: [<0000000057aa0dae>] cpuhp_thread_fun+0x13c/0x258
> > irq event stamp: 28
> > hardirqs last enabled at (27): [<000000000b861658>] _raw_spin_unlock_irq+0x38/0x58
> > hardirqs last disabled at (28): [<000000006231cfb1>] cpuhp_thread_fun+0xd0/0x258
> > softirqs last enabled at (0): [<0000000054d9737a>] copy_process.isra.32.part.33+0x450/0x1480
> > softirqs last disabled at (0): [< (null)>] (null)
> > CPU: 0 PID: 12 Comm: cpuhp/0 Not tainted 4.15.0+ #18
> > Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.25 Oct 17 2016
> > Call trace:
> > dump_backtrace+0x0/0x188
> > show_stack+0x24/0x2c
> > dump_stack+0xa4/0xe0
> > ___might_sleep+0x208/0x234
> > __might_sleep+0x58/0x8c
> > kmem_cache_alloc_trace+0x248/0x3e0
> > armpmu_alloc+0x38/0x1a8
> > arm_pmu_acpi_cpu_starting+0x11c/0x15c
> > cpuhp_invoke_callback+0x120/0x100c
> > cpuhp_thread_fun+0xe8/0x258
> > smpboot_thread_fn+0x170/0x268
> > kthread+0x110/0x13c
> > ret_from_fork+0x10/0x18
>
> I have patches to address this:
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2018-February/557838.html
> https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/acpi-pmu-lockdep

Awesome, I completely missed that. Thanks.

>
> > With commit 7d88eb695a1f ("arm/perf: Convert to hotplug state machine"),
> > arm_pmu uses the cpuhotplug framework to initialize the PMU driver when
> > using ACPI. However, the arm_pmu_acpi_cpu_starting() callback comes
> > before CPUHP_AP_ONLINE is reached which means it runs with interrupts
> > diabled and tries to allocate memory with GFP_KERNEL alloc which may
> > sleep.
> >
> > Move CPUHP_AP_PERF_ARM_ACPI_STARTING to come after CPUHP_AP_ONLINE so
> > that the arm_pmu initialization runs with interrupts enabled as it
> > does when booting with device tree.
> >
> > Fixes: 7d88eb695a1f ("arm/perf: Convert to hotplug state machine")
> > Signed-off-by: Mark Salter <msalter@redhat.com>
> > ---
> > include/linux/cpuhotplug.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index 5172ad0..e07b2da 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -114,7 +114,6 @@ enum cpuhp_state {
> > CPUHP_AP_ARM_VFP_STARTING,
> > CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
> > CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
> > - CPUHP_AP_PERF_ARM_ACPI_STARTING,
> > CPUHP_AP_PERF_ARM_STARTING,
> > CPUHP_AP_ARM_L2X0_STARTING,
> > CPUHP_AP_ARM_ARCH_TIMER_STARTING,
> > @@ -146,6 +145,7 @@ enum cpuhp_state {
> > CPUHP_AP_SMPBOOT_THREADS,
> > CPUHP_AP_X86_VDSO_VMA_ONLINE,
> > CPUHP_AP_IRQ_AFFINITY_ONLINE,
> > + CPUHP_AP_PERF_ARM_ACPI_STARTING,
>
> We need CPUHP_AP_PERF_ARM_ACPI_STARTING to happen before
> CPUHP_AP_PERF_ARM_STARTING, and I think this re-ordering prevents us
> from correctly resetting the PMU and enabling percpu interrupts, at
> least in heterogeneous configurations (e.g. big.LITTLE systems like
> Juno).
>
> I'm not sure whether we could safely move both callbacks this late.
>
> Thanks,
> Mark.

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