Hi Steven, Sebastian, Thank you for your review and explanation. You are absolutely right. I overlooked the case of PREEMPT_RT. I will look into other possible optimization methods later.
Best regards, Yongliang On Tue, Nov 11, 2025 at 4:13 PM Sebastian Andrzej Siewior <[email protected]> wrote: > > On 2025-11-10 18:38:54 [-0500], Steven Rostedt wrote: > > On Wed, 15 Oct 2025 19:49:52 +0800 > > Yongliang Gao <[email protected]> wrote: > > > > > diff --git a/kernel/trace/pid_list.c b/kernel/trace/pid_list.c > > > index 090bb5ea4a19..62082a4f60db 100644 > > > --- a/kernel/trace/pid_list.c > > > +++ b/kernel/trace/pid_list.c > > > @@ -138,14 +138,14 @@ bool trace_pid_list_is_set(struct trace_pid_list > > > *pid_list, unsigned int pid) > > > if (pid_split(pid, &upper1, &upper2, &lower) < 0) > > > return false; > > > > > > - raw_spin_lock_irqsave(&pid_list->lock, flags); > > > + read_lock_irqsave(&pid_list->lock, flags); > > > upper_chunk = pid_list->upper[upper1]; > > > if (upper_chunk) { > > > lower_chunk = upper_chunk->data[upper2]; > > > if (lower_chunk) > > > ret = test_bit(lower, lower_chunk->data); > > > } > > > - raw_spin_unlock_irqrestore(&pid_list->lock, flags); > > > + read_unlock_irqrestore(&pid_list->lock, flags); > > > > > > return ret; > > > } > > > > Unfortunately you cannot do this because this is called while holding the > > task pi_lock and rq locks. In PREEMPT_RT() the read/write_lock_* turn into > > mutexes. > > > > Sebastian, is there any equivalent of raw_read/write_locks() that can be > > used? > > Nope, no read-write lock that can be used in atomic sections. Well, > there is RCU. > > > -- Steve > > Sebastian
