srcu: Restrict atomic-SRCU non_block annotation to task context

srcu_read_lock_atomic() and srcu_read_unlock_atomic() arm and disarm
might_sleep() checks via non_block_start()/non_block_end(), skipping
hardirq so the update does not land on the interrupted task's
->non_block_count.

Inline softirqs run on the interrupted task's stack as well, so a
timer callback running atomic-SRCU readers races with the interrupted
task's own ->non_block_count updates, as KCSAN reports:

	BUG: KCSAN: data-race in srcu_torture_read_lock / srcu_torture_read_unlock

	write to 0xffffa00f818ea418 of 4 bytes by interrupt on cpu 0:
		srcu_torture_read_lock+0x422/0x470
		rcutorture_one_extend+0xdc/0x600
		rcu_torture_one_read+0xd1/0x330
		rcu_torture_timer+0x75/0x140
		call_timer_fn+0xe6/0x2f0
		...
		run_timer_softirq+0xb7/0x130
		handle_softirqs+0xfc/0x3f0
		__irq_exit_rcu+0x8e/0x100

Use in_task() so the annotation is applied only in task context; it
is redundant elsewhere because might_sleep() already warns about
sleeping from atomic context.

Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

0 files changed, 0 insertions, 0 deletions