From 0356d4e66214569de674ab2684f2e0b440a466ab Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 17 May 2022 11:30:32 -0700 Subject: rcu-tasks: Track blocked RCU Tasks Trace readers This commit places any task that has ever blocked within its current RCU Tasks Trace read-side critical section on a per-CPU list within the rcu_tasks_percpu structure. Tasks are removed from this list when they exit by the exit_tasks_rcu_finish_trace() function. The purpose of this commit is to provide the information needed to eliminate the current scan of the full task list. This commit offsets the INT_MIN value for ->trc_reader_nesting with the new nesting level in order to avoid queueing tasks that are exiting their read-side critical sections. [ paulmck: Apply kernel test robot feedback. ] [ paulmck: Apply feedback from syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com ] Signed-off-by: Paul E. McKenney Tested-by: syzbot Tested-by: "Zhang, Qiang1" Cc: Peter Zijlstra Cc: Neeraj Upadhyay Cc: Eric Dumazet Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: KP Singh --- include/linux/rcupdate_trace.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/rcupdate_trace.h') diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index 6f9c35817398..9bc8cbb33340 100644 --- a/include/linux/rcupdate_trace.h +++ b/include/linux/rcupdate_trace.h @@ -75,7 +75,7 @@ static inline void rcu_read_unlock_trace(void) nesting = READ_ONCE(t->trc_reader_nesting) - 1; barrier(); // Critical section before disabling. // Disable IPI-based setting of .need_qs. - WRITE_ONCE(t->trc_reader_nesting, INT_MIN); + WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting); if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) { WRITE_ONCE(t->trc_reader_nesting, nesting); return; // We assume shallow reader nesting. -- cgit v1.2.3-73-gaa49b