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| author | Sechang Lim <rhkrqnwk98@gmail.com> | 2026-06-30 08:47:37 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-10-01 14:00:34 +0200 |
| commit | 53bc5c556b82a3ca32b62ba349c4511f91526b9f (patch) | |
| tree | 057715130eee2cafd1969224db3e02ad5f8fead2 /include/linux/workqueue_api.h | |
| parent | 4b1f75be23c4fb0016a102d1cb108ba355c4c00d (diff) | |
sched: Set TIF_NEED_RESCHED before calling __trace_set_need_resched()
set_tsk_need_resched() tests TIF_NEED_RESCHED, calls
__trace_set_need_resched() if the flag is clear, then sets it via
set_tsk_thread_flag(). A BPF raw_tp program attached to
sched_set_need_resched executes synchronously inside __bpf_trace_run().
On return, __bpf_trace_run() drops the RCU lock with
rcu_read_unlock_migrate(), which on the preempt-or-BH-disabled path
calls set_need_resched_current() -> set_tsk_need_resched() again.
set_tsk_thread_flag() follows the tracepoint call, so every re-entrant
frame sees TIF_NEED_RESCHED clear and calls __trace_set_need_resched()
again:
BUG: TASK stack guard page was hit at ffffc9001224ff98
Oops: stack guard page: 0000 [#1] SMP KASAN PTI
RIP: 0010:__bpf_trace_sched_set_need_resched_tp+0x1c/0x190
Call Trace:
trace_sched_set_need_resched_tp+0x110/0x130
set_tsk_need_resched include/linux/sched.h:2076
set_need_resched_current include/linux/sched.h:2094
rcu_read_unlock_special+0x43a/0x440
__rcu_read_unlock+0x9e/0x120
rcu_read_unlock_migrate+0xa9/0x240
__bpf_trace_run+0x131/0x180
bpf_trace_run3+0x333/0x430
__bpf_trace_sched_set_need_resched_tp+0x13a/0x190
trace_sched_set_need_resched_tp+0x110/0x130
set_tsk_need_resched include/linux/sched.h:2076
...
__resched_curr() has the same ordering, firing the tracepoint before
setting the flag via set_ti_thread_flag() or set_nr_and_not_polling().
Fix it for consistency.
Replace the separate test_tsk_thread_flag() + set_tsk_thread_flag() pair
in set_tsk_need_resched() with test_and_set_tsk_thread_flag(). In
__resched_curr(), move the tracepoint call after the flag is set in
each path.
Fixes: adcc3bfa8806 ("sched: Adapt sched tracepoints for RV task model")
Signed-off-by: Sechang Lim <rhkrqnwk98@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Gabriele Monaco <gmonaco@redhat.com>
Link: https://patch.msgid.link/20260630084750.2792851-1-rhkrqnwk98@gmail.com
Diffstat (limited to 'include/linux/workqueue_api.h')
0 files changed, 0 insertions, 0 deletions