printk: Release console_sem after logbuf_lock
Release console_sem after unlocking the logbuf_lock so that we don't generate wakeups while holding logbuf_lock. This avoids some lock inversion troubles once we remove the lockdep_off bits between logbuf_lock and rq->lock (prints while holding rq->lock vs doing wakeups while holding logbuf_lock). There's of course still an actual deadlock where the printk()s under rq->lock will issue a wakeup from the up() call, but lockdep won't warn about that since semaphores are not tracked. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-j8swthl12u73h4znbvitljzd@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -782,7 +782,7 @@ static inline int can_use_console(unsigned int cpu)
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static int console_trylock_for_printk(unsigned int cpu)
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static int console_trylock_for_printk(unsigned int cpu)
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__releases(&logbuf_lock)
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__releases(&logbuf_lock)
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{
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{
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int retval = 0;
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int retval = 0, wake = 0;
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if (console_trylock()) {
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if (console_trylock()) {
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retval = 1;
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retval = 1;
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@ -795,12 +795,14 @@ static int console_trylock_for_printk(unsigned int cpu)
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*/
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*/
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if (!can_use_console(cpu)) {
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if (!can_use_console(cpu)) {
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console_locked = 0;
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console_locked = 0;
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up(&console_sem);
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wake = 1;
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retval = 0;
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retval = 0;
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}
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}
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}
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}
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printk_cpu = UINT_MAX;
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printk_cpu = UINT_MAX;
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spin_unlock(&logbuf_lock);
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spin_unlock(&logbuf_lock);
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if (wake)
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up(&console_sem);
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return retval;
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return retval;
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}
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}
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static const char recursion_bug_msg [] =
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static const char recursion_bug_msg [] =
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@ -1271,8 +1273,8 @@ void console_unlock(void)
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if (unlikely(exclusive_console))
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if (unlikely(exclusive_console))
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exclusive_console = NULL;
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exclusive_console = NULL;
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up(&console_sem);
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spin_unlock_irqrestore(&logbuf_lock, flags);
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spin_unlock_irqrestore(&logbuf_lock, flags);
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up(&console_sem);
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if (wake_klogd)
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if (wake_klogd)
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wake_up_klogd();
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wake_up_klogd();
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}
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}
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