* [PATCH v3] arch/arm64: Fix topology initialization for core scheduling
@ 2022-03-31 15:39 Phil Auld
2022-04-04 10:10 ` Will Deacon
0 siblings, 1 reply; 3+ messages in thread
From: Phil Auld @ 2022-03-31 15:39 UTC (permalink / raw)
To: linux-kernel
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Peter Zijlstra,
linux-arm-kernel, Dietmar Eggemann
Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()
to transfer the toplogy to the various cpu masks. This needs to be done
before the call to notify_cpu_starting() which tells the scheduler about
each cpu found, otherwise the core scheduling data structures are setup
in a way that does not match the actual topology.
With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`
for !leaders in:
notify_cpu_starting()
cpuhp_invoke_callback_range()
sched_cpu_starting()
sched_core_cpu_starting()
which leads to rq->core not being correctly set for !leader-rq's.
Without this change stress-ng (which enables core scheduling in its prctl
tests in newer versions -- i.e. with PR_SCHED_CORE support) causes a warning
and then a crash (trimmed for legibility):
[ 1853.805168] ------------[ cut here ]------------
[ 1853.809784] task_rq(b)->core != rq->core
[ 1853.809792] WARNING: CPU: 117 PID: 0 at kernel/sched/fair.c:11102 cfs_prio_less+0x1b4/0x1c4
...
[ 1854.015210] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
...
[ 1854.231256] Call trace:
[ 1854.233689] pick_next_task+0x3dc/0x81c
[ 1854.237512] __schedule+0x10c/0x4cc
[ 1854.240988] schedule_idle+0x34/0x54
Fixes: 9edeaea1bc45 ("sched: Core-wide rq->lock")
Signed-off-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
This is a similar issue to
f2703def339c ("MIPS: smp: fill in sibling and core maps earlier")
which fixed it for MIPS.
v2: Fixed the commit message. No code change.
arch/arm64/kernel/smp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 27df5c1e6baa..3b46041f2b97 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -234,6 +234,7 @@ asmlinkage notrace void secondary_start_kernel(void)
* Log the CPU info before it is marked online and might get read.
*/
cpuinfo_store_cpu();
+ store_cpu_topology(cpu);
/*
* Enable GIC and timers.
@@ -242,7 +243,6 @@ asmlinkage notrace void secondary_start_kernel(void)
ipi_setup(cpu);
- store_cpu_topology(cpu);
numa_add_cpu(cpu);
/*
--
2.18.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] arch/arm64: Fix topology initialization for core scheduling
2022-03-31 15:39 [PATCH v3] arch/arm64: Fix topology initialization for core scheduling Phil Auld
@ 2022-04-04 10:10 ` Will Deacon
2022-04-04 14:26 ` Phil Auld
0 siblings, 1 reply; 3+ messages in thread
From: Will Deacon @ 2022-04-04 10:10 UTC (permalink / raw)
To: linux-kernel, Phil Auld
Cc: catalin.marinas, kernel-team, Will Deacon, Dietmar Eggemann,
Mark Rutland, Peter Zijlstra, linux-arm-kernel
On Thu, 31 Mar 2022 11:39:26 -0400, Phil Auld wrote:
> Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()
> to transfer the toplogy to the various cpu masks. This needs to be done
> before the call to notify_cpu_starting() which tells the scheduler about
> each cpu found, otherwise the core scheduling data structures are setup
> in a way that does not match the actual topology.
>
> With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`
> for !leaders in:
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arch/arm64: Fix topology initialization for core scheduling
https://git.kernel.org/arm64/c/5524cbb1bfcd
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] arch/arm64: Fix topology initialization for core scheduling
2022-04-04 10:10 ` Will Deacon
@ 2022-04-04 14:26 ` Phil Auld
0 siblings, 0 replies; 3+ messages in thread
From: Phil Auld @ 2022-04-04 14:26 UTC (permalink / raw)
To: Will Deacon
Cc: linux-kernel, catalin.marinas, kernel-team, Dietmar Eggemann,
Mark Rutland, Peter Zijlstra, linux-arm-kernel
On Mon, Apr 04, 2022 at 11:10:48AM +0100 Will Deacon wrote:
> On Thu, 31 Mar 2022 11:39:26 -0400, Phil Auld wrote:
> > Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()
> > to transfer the toplogy to the various cpu masks. This needs to be done
> > before the call to notify_cpu_starting() which tells the scheduler about
> > each cpu found, otherwise the core scheduling data structures are setup
> > in a way that does not match the actual topology.
> >
> > With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`
> > for !leaders in:
> >
> > [...]
>
> Applied to arm64 (for-next/fixes), thanks!
>
Thanks, Will!
Cheers,
Phil
> [1/1] arch/arm64: Fix topology initialization for core scheduling
> https://git.kernel.org/arm64/c/5524cbb1bfcd
>
> Cheers,
> --
> Will
>
> https://fixes.arm64.dev
> https://next.arm64.dev
> https://will.arm64.dev
>
--
^ permalink raw reply [flat|nested] 3+ messages in thread
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