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 [email protected] ]

Signed-off-by: Paul E. McKenney <[email protected]>
Tested-by: syzbot <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: KP Singh <[email protected]>

0 files changed, 0 insertions, 0 deletions