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[dm-devel] FW: Re: [PATCH 2/3] check for completed exception after dropped lock



----- Forwarded message from Mikulas Patocka <mpatocka redhat com> -----

Date: Wed, 25 Feb 2009 14:26:08 -0500 (EST)
From: Mikulas Patocka <mpatocka redhat com>
Subject: Re: [PATCH 2/3] check for completed exception after dropped lock
To: dm-devek redhat com
cc: Alasdair G Kergon <agk redhat com>

> -	up_write(&s->lock);
> -	pe = alloc_pending_exception(s);
> -	down_write(&s->lock);

BTW. shouldn't this rw-semaphore be replaced with a mutex or normal 
semaphore? It is never locked for read. (it used to be in locked for reads 
in RHEL-4). Mutex has better performance than a rw-semaphore --- it takes 
fewer cycles and it also guarantees first-in-first-out ordering.

Mikulas


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