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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jul 2025 04:16:29.0405 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f60e0819-9385-4ed5-da76-08ddc99fb2ad X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF000099DF.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4220 On 7/16/2025 4:10 PM, Peter Zijlstra wrote: > On Wed, Jul 16, 2025 at 08:53:01AM +0200, Beata Michalska wrote: >> Wouldn't it be enough to use SEQCNT_ZERO? Those are static per-cpu ones. > > Yeah, I suppose that should work. The below builds, but I've not yet > observed the issue myself. > > --- > Subject: sched/psi: Fix psi_seq initialization > From: Peter Zijlstra > Date: Tue, 15 Jul 2025 15:11:14 -0400 > > With the seqcount moved out of the group into a global psi_seq, > re-initializing the seqcount on group creation is causing seqcount > corruption. > > Fixes: 570c8efd5eb7 ("sched/psi: Optimize psi_group_change() cpu_clock() usage") > Reported-by: Chris Mason > Suggested-by: Beata Michalska > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/sched/psi.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > --- a/kernel/sched/psi.c > +++ b/kernel/sched/psi.c > @@ -176,7 +176,7 @@ struct psi_group psi_system = { > .pcpu = &system_group_pcpu, > }; > > -static DEFINE_PER_CPU(seqcount_t, psi_seq); > +static DEFINE_PER_CPU(seqcount_t, psi_seq) = SEQCNT_ZERO(psi_seq); > > static inline void psi_write_begin(int cpu) > { > @@ -204,11 +204,7 @@ static void poll_timer_fn(struct timer_l > > static void group_init(struct psi_group *group) > { > - int cpu; > - > group->enabled = true; > - for_each_possible_cpu(cpu) > - seqcount_init(per_cpu_ptr(&psi_seq, cpu)); > group->avg_last_update = sched_clock(); > group->avg_next_update = group->avg_last_update + psi_period; > mutex_init(&group->avgs_lock); I've tested the above patch, and it resolves the issue. Could we include this patch in the linux-next builds? We have been encountering the reported issue regularly in our daily CI. Tested-by: Srikanth Aithal