From: Rusty Russell Prevent errors in boot when cpus_possible() contains a cpu which is not online (ie. a cpu didn't come up). This doesn't happen on x86, since a boot failure makes that CPU no longer possible (hacky, but it works). When the cpu fails to come up, some callbacks do kthread_stop(), which doesn't work without keventd (which hasn't started yet). Call it directly, and take care that it restores signal state (note: do_sigaction does a flush on blocked signals, so we don't need to repeat it). --- kernel/kthread.c | 27 +++++++++++++++------------ 1 files changed, 15 insertions(+), 12 deletions(-) diff -puN kernel/kthread.c~kthread-handle-non-booting-CPUs kernel/kthread.c --- 25/kernel/kthread.c~kthread-handle-non-booting-CPUs 2004-02-16 23:40:30.000000000 -0800 +++ 25-akpm/kernel/kthread.c 2004-02-16 23:40:30.000000000 -0800 @@ -101,15 +101,16 @@ static void keventd_stop_kthread(void *_ { struct kthread_stop_info *stop = _stop; int status, pid; - sigset_t blocked; - struct k_sigaction sa; + sigset_t chldonly, oldset; + struct k_sigaction sa, oldsa; /* Install a handler so SIGCHLD is actually delivered */ sa.sa.sa_handler = SIG_DFL; sa.sa.sa_flags = 0; siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); - do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); - allow_signal(SIGCHLD); + siginitset(&chldonly, sigmask(SIGCHLD)); + do_sigaction(SIGCHLD, &sa, &oldsa); + sigprocmask(SIG_UNBLOCK, &chldonly, &oldset); adopt_kthread(stop->k); /* Grab pid now: after waitpid(), stop->k is invalid. */ @@ -124,12 +125,9 @@ static void keventd_stop_kthread(void *_ stop->result = -((status >> 8) & 0xFF); complete(&stop->done); - /* Back to normal: block and flush all signals */ - sigfillset(&blocked); - sigprocmask(SIG_BLOCK, &blocked, NULL); - flush_signals(current); - sa.sa.sa_handler = SIG_IGN; - do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); + /* Return to normal, then reap any children who died in the race. */ + sigprocmask(SIG_SETMASK, &oldset, NULL); + do_sigaction(SIGCHLD, &oldsa, NULL); while (waitpid(-1, &status, __WALL|WNOHANG) > 0); } @@ -180,7 +178,12 @@ int kthread_stop(struct task_struct *k) stop.k = k; init_completion(&stop.done); - schedule_work(&work); - wait_for_completion(&stop.done); + /* At boot, if CPUs fail to come up, this happens. */ + if (!keventd_up()) + work.func(work.data); + else { + schedule_work(&work); + wait_for_completion(&stop.done); + } return stop.result; } _