Messages in this thread |  | | | From | David Woodhouse <> | | Subject | Re: [CHECKER] a couple potential deadlocks in 2.4.5-ac8 | | Date | Sun, 10 Jun 2001 12:59:29 +0100 |
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rusty@rustcorp.com.au said: > In message <19317.992115181@redhat.com> you write: > > torvalds@transmeta.com said: > > > Good point. Spinlocks (with the exception of read-read locks, of > > > course) and semaphores will deadlock on recursive use, while the BKL > > > has this "process usage counter" recursion protection. > > > > Obtaining a read lock twice can deadlock too, can't it > > Or do we not make new readers sleep if there's a writer waiting? > > We can never[1] make new readers sleep if there's a writer waiting, as > Linus guaranteed that an IRQ handler which only ever grabs a read lock > means the rest of the code doesn't need to block interrupts on its > read locks (see Documentation/spinlock.txt IIRC).
You're right. Despite the fact that upon closer examination it's obvious that Linus was only referring to rw-spinlocks as safe, I was actually thinking of rw-semaphores.
-- dwmw2
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