linux-kernel - Re: drivers/char/random.c:write_pool() -- cond

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Message-ID: <20071203184958.GN17536@waste.org>
Date:	Mon, 3 Dec 2007 12:49:59 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Linux kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: drivers/char/random.c:write_pool() -- cond_resched needed?

On Fri, Nov 30, 2007 at 11:58:10PM +0200, Sami Farin wrote:
> In write_pool(), isn't cond_resched() needed after call to
> add_entropy_words() because otherwise there can be large latencies
> (think of command "dd if=/dev/zero of=/dev/random bs=100000000" ) ?

Yes, looks like you're right.

Reduce latency for large writes to /dev/[u]random

Signed-off-by: Matt Mackall <mpm@...enic.com>

diff -r c60016ba6237 drivers/char/random.c
--- a/drivers/char/random.c	Tue Nov 13 09:09:36 2007 -0800
+++ b/drivers/char/random.c	Mon Dec 03 12:48:30 2007 -0600
@@ -1041,6 +1041,7 @@ write_pool(struct entropy_store *r, cons
 		p += bytes;
 
 		add_entropy_words(r, buf, (bytes + 3) / 4);
+		cond_resched();
 	}
 
 	return 0;


-- 
Mathematics is the supreme nostalgia of our time.
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