Messages in this thread | | | Date | Sun, 7 Feb 1999 11:01:33 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Linux-2.2.2-pre2.. |
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On Sun, 7 Feb 1999, Andrea Arcangeli wrote: > > It still seems that do_tty_hangup() is racing with the other CPU due > lock_kernel() that does nothing,
No, do_tty_hangup() will never be called asynchronously: it will always be called from a synchronous kernel context (either from within the scheduler or from processes that do a run_task_queue() on their own).
If the caller already held the kernel lock, lock_kernel() is indeed a no-op, but that's how it's designed: it doesn't need to do anything at that point.
Basically, the problem is not the kernel lock itself - everything we do runs with the kernel lock held (either gotten by do_tty_hangup(), or by the entity that called it). The problem is that we cache a "tty" pointer in between lock domains - so even though everything holds the kernel lock, there is nothing that validates that the pointer is not stale.
Linus
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