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McKenney" > Cc: Boqun Feng > Cc: stable@vger.kernel.org > --- > include/linux/rseq.h | 11 ++++++++--- > kernel/rseq.c | 10 +++++----- > 2 files changed, 13 insertions(+), 8 deletions(-) > > --- a/include/linux/rseq.h > +++ b/include/linux/rseq.h > @@ -7,6 +7,12 @@ > #include > #include > > +#ifdef CONFIG_MEMBARRIER > +# define RSEQ_EVENT_GUARD irq > +#else > +# define RSEQ_EVENT_GUARD preempt > +#endif We should also update this comment in include/linux/sched.h: /* * RmW on rseq_event_mask must be performed atomically * with respect to preemption. */ unsigned long rseq_event_mask; to e.g.: /* * RmW on rseq_event_mask must be performed atomically * with respect to preemption and membarrier IPIs. */ > + > /* > * Map the event mask on the user-space ABI enum rseq_cs_flags > * for direct mask checks. > @@ -41,9 +47,8 @@ static inline void rseq_handle_notify_re > static inline void rseq_signal_deliver(struct ksignal *ksig, > struct pt_regs *regs) > { > - preempt_disable(); > - __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); > - preempt_enable(); > + scoped_guard(RSEQ_EVENT_GUARD) > + __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); Then we have more to worry about interaction of the following rseq events with membarrier IPI: - rseq_preempt, rseq_migrate, rseq_signal_deliver. Both rseq_preempt and rseq_migrate are documented as only being required to be called with preempt off, not irq off. I don't see the point in sharing the same rseq_event_mask across all of those rseq event sources. Can we just move the event sources requiring preempt-off to their own word, and use a separate word for membarrier IPI instead ? This would allow us to partition the problem into two distinct states each protected by their respective mechanism. > rseq_handle_notify_resume(ksig, regs); > } > > --- a/kernel/rseq.c > +++ b/kernel/rseq.c > @@ -342,12 +342,12 @@ static int rseq_need_restart(struct task > > /* > * Load and clear event mask atomically with respect to > - * scheduler preemption. > + * scheduler preemption and membarrier IPIs. > */ > - preempt_disable(); > - event_mask = t->rseq_event_mask; > - t->rseq_event_mask = 0; > - preempt_enable(); > + scoped_guard(RSEQ_EVENT_GUARD) { > + event_mask = t->rseq_event_mask; > + t->rseq_event_mask = 0; > + } Instead we could sample both the preempt-off and the irq-off words here. Thanks, Mathieu > > return !!event_mask; > } -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com