Messages in this thread Patch in this message | | | From | Tony Luck <> | Subject | [PATCH] x86/resctrl: Fix mbm_setup_overflow_handler() when last CPU goes offline | Date | Wed, 27 Mar 2024 11:46:19 -0700 |
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Don't bother looking for another CPU to take over MBM overflow duties when the last CPU in a domain goes offline. Doing so results in this Oops:
[ 97.166136] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 97.173118] #PF: supervisor read access in kernel mode [ 97.178263] #PF: error_code(0x0000) - not-present page [ 97.183410] PGD 0 [ 97.185438] Oops: 0000 [#1] PREEMPT SMP NOPTI [ 97.189805] CPU: 36 PID: 235 Comm: cpuhp/36 Tainted: G T 6.9.0-rc1 #356 [ 97.208322] RIP: 0010:__find_nth_andnot_bit+0x66/0x110
Fixes: 978fcca954cb ("x86/resctrl: Allow overflow/limbo handlers to be scheduled on any-but CPU") Signed-off-by: Tony Luck <tony.luck@intel.com> --- arch/x86/kernel/cpu/resctrl/monitor.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c index 757d475158a3..4d9987acffd6 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -929,6 +929,10 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms, unsigned long delay = msecs_to_jiffies(delay_ms); int cpu; + /* Nothing to do if this is the last CPU in a domain going offline */ + if (!delay_ms && bitmap_weight(cpumask_bits(&dom->cpu_mask), nr_cpu_ids) == 1) + return; + /* * When a domain comes online there is no guarantee the filesystem is * mounted. If not, there is no need to catch counter overflow. -- 2.44.0
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