| From 2fe5cbc9978bd9dc05eeb7348bb96e6df9d0497f Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Thu, 31 Mar 2022 11:39:26 -0400 |
| Subject: arch/arm64: Fix topology initialization for core scheduling |
| |
| From: Phil Auld <pauld@redhat.com> |
| |
| [ Upstream commit 5524cbb1bfcdff0cad0aaa9f94e6092002a07259 ] |
| |
| 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> |
| Link: https://lore.kernel.org/r/20220331153926.25742-1-pauld@redhat.com |
| Signed-off-by: Will Deacon <will@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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); |
| |
| /* |
| -- |
| 2.35.1 |
| |
