tree 94b417d4f373570f43c3c9de06f542bc8aa0c7e9
parent f23e76a32dbfc45418a1448f94886eb608b35b98
author Oleg Nesterov <oleg@redhat.com> 1757848148 +0200
committer Andrew Morton <akpm@linux-foundation.org> 1758597059 -0700

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>