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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 2IAlyRRKSVq0d5H0kOu0Q0/Q1PWfpMfvZTeN9CuhlVFgIp0po/wtE477gup1mYOPdWUqKYINPMMWq317Mety7KkqdLCAsFY3aGnYh7kDp/TeBsyKwEO2OdcbvQOwb8bZbtF1kgTjfNixA883/I0Cxm9Awk0nWCbg85sR5PBgL/A6E4fLyfi6Zc9ODqc1Tm6vDIoW136A/ixuCOHiWtPmU4XRslw+HcM9aOHCYdboHGRtF1D3pyZORF+cakcpcI4756kkimDTiDuIFv6naY3vKXZ6c7OoGbGHijuaPjYclTyMqpvpKaj4tJkPA9aal9BYcsSDkgmecO4lB2zEKxoru46vKBeK9rpXrfoZSZxNyjU/DGMthVO82EbZjRZDdlfk1rWTY+eU5xe3J3k2SHOgPSE/WlHvrIyBo6oDT7RqBqCRhIWVMvB1w9zvlkyAKYOZ X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 May 2026 16:38:13.8586 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ad859064-7006-4254-38ee-08dead2032fa 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00005FFD.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9687 Hello Ruidong, On 5/8/2026 11:45 AM, Ruidong Tian wrote: > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 368c7b4d7cb5..d9ee2381c3a3 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -836,6 +836,11 @@ struct task_struct { > */ > randomized_struct_fields_start > > +#ifdef CONFIG_STACKPROTECTOR > + /* Canary value for the -fstack-protector GCC feature: */ > + unsigned long stack_canary; > +#endif So I'm looking at pahole and I see the following on mainline (v7.1-rc2): struct task_struct { struct thread_info thread_info; /* 0 24 */ unsigned int __state; /* 24 4 */ unsigned int saved_state; /* 28 4 */ void * stack; /* 32 8 */ refcount_t usage; /* 40 4 */ unsigned int flags; /* 44 4 */ unsigned int ptrace; /* 48 4 */ int on_cpu; /* 52 4 */ struct __call_single_node wake_entry; /* 56 16 */ /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ unsigned int wakee_flips; /* 72 4 */ /* XXX 4 bytes hole, try to pack */ long unsigned int wakee_flip_decay_ts; /* 80 8 */ struct task_struct * last_wakee; /* 88 8 */ int recent_used_cpu; /* 96 4 */ int wake_cpu; /* 100 4 */ int on_rq; /* 104 4 */ int prio; /* 108 4 */ int static_prio; /* 112 4 */ int normal_prio; /* 116 4 */ unsigned int rt_priority; /* 120 4 */ /* XXX 4 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ ... }; Except for alloc_tag, nothing in here is config dependent, and if we move "wakee_flips" to after "last_wakee", we open up 8 bytes in this cache line and "stack_canary" should be able to fit in there without needing any additional space wrt to where we are at. It'll look like: struct task_struct { ... int on_cpu; /* 52 4 */ struct __call_single_node wake_entry; /* 56 16 */ /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ unsigned long stack_canary; /* 72 8 */ long unsigned int wakee_flip_decay_ts; /* 80 8 */ struct task_struct * last_wakee; /* 88 8 */ unsigned int wakee_flips; /* 96 4 */ ... } An offset of 72 bytes should be fine right? I doubt we'll ever add 2KB worth of data in this area to worry about this again. > + > void *stack; > refcount_t usage; > /* Per task flags (PF_*), defined further below: */ -- Thanks and Regards, Prateek