Messages in this thread | | | Date | Thu, 21 Oct 2004 12:03:12 +0200 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8 |
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* Christoph Hellwig <hch@infradead.org> wrote:
> > yes, it is valid and perfectly fine code, but i'm trying to separate out > > the simple 'mutex' functionality (99% of the semaphore users are just > > that) and implement a 'counted semaphore' separately. This removes a > > number of implementational constraints from mutexes. > > So leave the good old struct semaphore alone and introduce a mutex_t..
with nearly 1000 'struct semaphore' references in the kernel and 980 of them being simple mutex use this is rather impractical. So i instead went for safely detecting the 20 non-mutex uses and converting those places. (Btw., 90% of those 20 cases can be detected safely at compile-time (and link-time) by removing DECLARE_MUTEX_LOCKED and making sema_init() a macro that only allows constant values of 0 and 1 and produces a link error for other cases.)
this work is still incomplete so i'm not arguing for upstream inclusion.
(But while we did this a couple of places did turn out to use semaphores for completion which is inefficient - we converted those to completions and are contributing those changes to mainline. But this issue is totally orthogonal to the issue of counted semaphores.)
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