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in the patch 0b5e1c5255e7ee8670e077e8224e5c2281229a5b, it releases console_sem after logbuf_lock, the description of this patch is as below:
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. could you please give me a detail example about the issue it tries to fix? thanks. |
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