• Oleg Nesterov's avatar
    [PATCH] introduce lock_task_sighand() helper · f63ee72e
    Oleg Nesterov authored
    Add lock_task_sighand() helper and converts group_send_sig_info() to use
    it.  Hopefully we will have more users soon.
    
    This patch also removes '!sighand->count' and '!p->usage' checks, I think
    they both are bogus, racy and unneeded (but probably it makes sense to
    restore them as BUG_ON()s).
    
    ->sighand is cleared and it's ->count is decremented in release_task() with
    sighand->siglock held, so it is a bug to have '!p->usage || !->count' after
    we already locked and verified it is the same.  On the other hand, an
    already dead task without ->sighand can have a non-zero ->usage due to
    ptrace, for example.
    
    If we read the stale value of ->sighand we must see the change after
    spin_lock(), because that change was done while holding that same old
    ->sighand.siglock.
    Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    f63ee72e
signal.c 70.6 KB