Paul E. McKenney d93ba6e46e rcu-tasks: Add trc_inspect_reader() checks for exiting critical section
commit 18f08e758f upstream.

Currently, trc_inspect_reader() treats a task exiting its RCU Tasks
Trace read-side critical section the same as being within that critical
section.  However, this can fail because that task might have already
checked its .need_qs field, which means that it might never decrement
the all-important trc_n_readers_need_end counter.  Of course, for that
to happen, the task would need to never again execute an RCU Tasks Trace
read-side critical section, but this really could happen if the system's
last trampoline was removed.  Note that exit from such a critical section
cannot be treated as a quiescent state due to the possibility of nested
critical sections.  This means that if trc_inspect_reader() sees a
negative nesting value, it must set up to try again later.

This commit therefore ignores tasks that are exiting their RCU Tasks
Trace read-side critical sections so that they will be rechecked later.

[ paulmck: Apply feedback from Neeraj Upadhyay and Boqun Feng. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-09-02 09:18:14 +02:00
2023-09-02 09:18:13 +02:00
2023-08-30 16:23:16 +02:00
2023-08-30 16:23:09 +02:00
2023-04-05 11:23:43 +02:00
2023-06-21 15:45:38 +02:00
2023-08-30 16:23:20 +02:00

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