Date: Thu, 26 Jan 2012 07:39:50 +0400 From: Andrey Chernov <ache@FreeBSD.ORG> To: Mark Murray <markm@FreeBSD.ORG>, David Schultz <das@FreeBSD.ORG>, src-committers@FreeBSD.ORG, svn-src-all@FreeBSD.ORG, svn-src-head@FreeBSD.ORG Subject: Re: svn commit: r230230 - head/sys/dev/random Message-ID: <20120126033950.GA80737@vniz.net> In-Reply-To: <20120126030305.GA80493@vniz.net> References: <E1Rny2A-000C3x-O6@groundzero.grondar.org> <20120120055823.GA28177@vniz.net> <E1RoG98-000DiP-0Y@groundzero.grondar.org> <20120120215649.GA40016@vniz.net> <E1Rp0lq-000Gly-FT@groundzero.grondar.org> <20120122185545.GA11874@vniz.net> <E1Rp5Bn-000HBl-2P@groundzero.grondar.org> <20120125140237.GA74896@vniz.net> <E1Rq8Kn-000Ms9-KE@groundzero.grondar.org> <20120126030305.GA80493@vniz.net>
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On Thu, Jan 26, 2012 at 07:03:05AM +0400, Andrey Chernov wrote:
> On Wed, Jan 25, 2012 at 07:16:41PM +0000, Mark Murray wrote:
> > I thought you were going to do this as a function? It would be
> > slightly neater to do it that way.
> >
> > Looks good! Are you sure this needs no locking or volatile
> > variables?
>
> Now with function, volatile, atomic and even enum:
Sorry. Reading of state variable should be atomical too. Fixed version:
--- sys/libkern.h.old 2012-01-16 07:15:12.000000000 +0400
+++ sys/libkern.h 2012-01-26 06:01:51.000000000 +0400
@@ -72,6 +72,8 @@ static __inline quad_t qabs(quad_t a) {
/* Prototypes for non-quad routines. */
struct malloc_type;
+enum arc4_is { ARC4_ENTR_NONE, ARC4_ENTR_HAVE, ARC4_ENTR_DONE };
+void arc4rand_iniseed_state(enum arc4_is state);
uint32_t arc4random(void);
void arc4rand(void *ptr, u_int len, int reseed);
int bcmp(const void *, const void *, size_t);
--- dev/random/randomdev_soft.c.old 2011-03-02 01:42:19.000000000 +0300
+++ dev/random/randomdev_soft.c 2012-01-26 06:04:05.000000000 +0400
@@ -366,6 +366,7 @@ random_yarrow_unblock(void)
selwakeuppri(&random_systat.rsel, PUSER);
wakeup(&random_systat);
}
+ arc4rand_iniseed_state(ARC4_ENTR_HAVE);
}
static int
--- libkern/arc4random.c.old 2008-08-08 01:51:09.000000000 +0400
+++ libkern/arc4random.c 2012-01-26 07:27:06.000000000 +0400
@@ -24,6 +24,7 @@ __FBSDID("$FreeBSD: src/sys/libkern/arc4
#define ARC4_RESEED_SECONDS 300
#define ARC4_KEYBYTES (256 / 8)
+static volatile enum arc4_is iniseed_state = ARC4_ENTR_NONE;
static u_int8_t arc4_i, arc4_j;
static int arc4_numruns = 0;
static u_int8_t arc4_sbox[256];
@@ -74,6 +75,7 @@ arc4_randomstir (void)
/* Reset for next reseed cycle. */
arc4_t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
arc4_numruns = 0;
+ arc4rand_iniseed_state(ARC4_ENTR_DONE);
/*
* Throw away the first N words of output, as suggested in the
@@ -103,6 +105,24 @@ arc4_init(void)
SYSINIT(arc4_init, SI_SUB_LOCK, SI_ORDER_ANY, arc4_init, NULL);
+void
+arc4rand_iniseed_state(enum arc4_is state)
+{
+ switch (state) {
+ case ARC4_ENTR_NONE:
+ atomic_store_rel_int(&iniseed_state, state);
+ break;
+ case ARC4_ENTR_HAVE:
+ if (atomic_load_acq_int(&iniseed_state) == ARC4_ENTR_NONE)
+ atomic_store_rel_int(&iniseed_state, state);
+ break;
+ case ARC4_ENTR_DONE:
+ if (atomic_load_acq_int(&iniseed_state) == ARC4_ENTR_HAVE)
+ atomic_store_rel_int(&iniseed_state, state);
+ break;
+ }
+}
+
/*
* Generate a random byte.
*/
@@ -130,7 +150,7 @@ arc4rand(void *ptr, u_int len, int resee
struct timeval tv;
getmicrouptime(&tv);
- if (reseed ||
+ if (reseed || atomic_load_acq_int(&iniseed_state) == ARC4_ENTR_HAVE ||
(arc4_numruns > ARC4_RESEED_BYTES) ||
(tv.tv_sec > arc4_t_reseed))
arc4_randomstir();
--
http://ache.vniz.net/
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