sched/task.h: fix the wrong comment on task_lock() nesting with tasklist_lock
The ancient comment above task_lock() states that it can be nested outside
of read_lock(&tasklist_lock), but this is no longer true:
CPU_0 CPU_1 CPU_2
task_lock() read_lock(tasklist)
write_lock_irq(tasklist)
read_lock(tasklist) task_lock()
Unless CPU_0 calls read_lock() in IRQ context, queued_read_lock_slowpath()
won't get the lock immediately, it will spin waiting for the pending
writer on CPU_2, resulting in a deadlock.
Link: https://lkml.kernel.org/r/20250914110908.GA18769@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1 file changed
