Messages in this thread | | | Date | Mon, 19 Jun 2006 10:21:50 +0200 | From | Ingo Molnar <> | Subject | Re: [patch] increase spinlock-debug looping timeouts from 1 sec to 1 min |
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* Ingo Molnar <mingo@elte.hu> wrote:
> no. Write-locks are unfair too, and there's no guarantee that writes > are listened to. That's why nested read_lock() is valid, while nested > down_read() is invalid. > > Take a look at arch/i386/kernel/semaphore.c, __write_lock_failed() > just adds back the RW_LOCK_BIAS and retries in a loop. There's no > difference to an open-coded write_trylock loop - unless i'm missing > something fundamental.
did i ever mention that i find rwlocks evil, inefficient and bug-prone, and that we should get rid of them? :-)
(Most rwlock users can be converted to straight spinlocks just fine, but there are a couple of places that rely on read-lock nesting. The hardest-to-fix offenders are nested rcu_read_locks() in the netfilter code. I gave up converting them to saner locking, PREEMPT_RCU works it around in the -rt tree, by not being rwlock based.)
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