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

[Alasdair G Kergon]

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

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