• Oleg Nesterov's avatar
    task_work_add: generic process-context callbacks · e73f8959
    Oleg Nesterov authored
    Provide a simple mechanism that allows running code in the (nonatomic)
    context of the arbitrary task.
    
    The caller does task_work_add(task, task_work) and this task executes
    task_work->func() either from do_notify_resume() or from do_exit().  The
    callback can rely on PF_EXITING to detect the latter case.
    
    "struct task_work" can be embedded in another struct, still it has "void
    *data" to handle the most common/simple case.
    
    This allows us to kill the ->replacement_session_keyring hack, and
    potentially this can have more users.
    
    Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into
    tracehook_notify_resume() and do_exit().  But at the same time we can
    remove the "replacement_session_keyring != NULL" checks from
    arch/*/signal.c and exit_creds().
    
    Note: task_work_add/task_work_run abuses ->pi_lock.  This is only because
    this lock is already used by lookup_pi_state() to synchronize with
    do_exit() setting PF_EXITING.  Fortunately the scope of this lock in
    task_work.c is really tiny, and the code is unlikely anyway.
    Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
    Acked-by: default avatarDavid Howells <dhowells@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Richard Kuo <rkuo@codeaurora.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Alexander Gordeev <agordeev@redhat.com>
    Cc: Chris Zankel <chris@zankel.net>
    Cc: David Smith <dsmith@redhat.com>
    Cc: "Frank Ch. Eigler" <fche@redhat.com>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Cc: Larry Woodman <lwoodman@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    e73f8959
fork.c 44.3 KB