Re: Mutex vs semaphores scheduler bug
From: Peter Zijlstra
Date: Sat Oct 17 2009 - 11:32:56 EST
On Fri, 2009-10-16 at 00:44 +0100, David Howells wrote:
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > The problem appears to be that rwsem doesn't allow lock-stealing
> With good reason. rwsems can be read or write locked for a long time - so if
> readers can jump the queue on read-locked rwsems, then writer starvation is a
> real possibility. I carefully implemented it so that it is a strict FIFO to
> avoid certain problems I was having.
Well, it kinda sucks that rwsem is slower than a mutex.
What about allowing writer stealing when the next contending task is a
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