Module Name: src
Committed By: riastradh
Date: Tue Apr 21 03:53:07 UTC 2015
Modified Files:
src/sys/kern: kern_rndq.c
src/sys/sys: rndsource.h
Log Message:
Release rnd_global.lock while calling an rndsource's callback.
Obviates the need for obnoxious double-lock dances in hardware RNG
drivers.
To generate a diff of this commit:
cvs rdiff -u -r1.67 -r1.68 src/sys/kern/kern_rndq.c
cvs rdiff -u -r1.2 -r1.3 src/sys/sys/rndsource.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_rndq.c
diff -u src/sys/kern/kern_rndq.c:1.67 src/sys/kern/kern_rndq.c:1.68
--- src/sys/kern/kern_rndq.c:1.67 Tue Apr 21 03:46:46 2015
+++ src/sys/kern/kern_rndq.c Tue Apr 21 03:53:07 2015
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_rndq.c,v 1.67 2015/04/21 03:46:46 riastradh Exp $ */
+/* $NetBSD: kern_rndq.c,v 1.68 2015/04/21 03:53:07 riastradh Exp $ */
/*-
* Copyright (c) 1997-2013 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.67 2015/04/21 03:46:46 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.68 2015/04/21 03:53:07 riastradh Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
@@ -126,6 +126,7 @@ static struct {
kmutex_t lock;
rndpool_t pool;
LIST_HEAD(, krndsource) sources;
+ kcondvar_t cv;
} rnd_global __cacheline_aligned;
/*
@@ -260,15 +261,32 @@ rnd_schedule_wakeup(void)
void
rnd_getmore(size_t byteswanted)
{
- krndsource_t *rs;
+ krndsource_t *rs, *next;
mutex_spin_enter(&rnd_global.lock);
- LIST_FOREACH(rs, &rnd_global.sources, list) {
+ LIST_FOREACH_SAFE(rs, &rnd_global.sources, list, next) {
+ /* Skip if there's no callback. */
if (!ISSET(rs->flags, RND_FLAG_HASCB))
continue;
KASSERT(rs->get != NULL);
- KASSERT(rs->getarg != NULL);
+
+ /* Skip if there are too many users right now. */
+ if (rs->refcnt == UINT_MAX)
+ continue;
+
+ /*
+ * Hold a reference while we release rnd_global.lock to
+ * call the callback. The callback may in turn call
+ * rnd_add_data, which acquires rnd_global.lock.
+ */
+ rs->refcnt++;
+ mutex_spin_exit(&rnd_global.lock);
rs->get(byteswanted, rs->getarg);
+ mutex_spin_enter(&rnd_global.lock);
+ if (--rs->refcnt == 0)
+ cv_broadcast(&rnd_global.cv);
+
+ /* Dribble some goo to the console. */
rnd_printf_verbose("rnd: entropy estimate %zu bits\n",
rndpool_get_entropy_count(&rnd_global.pool));
rnd_printf_verbose("rnd: asking source %s for %zu bytes\n",
@@ -497,6 +515,7 @@ rnd_init(void)
mutex_init(&rnd_global.lock, MUTEX_DEFAULT, IPL_VM);
rndpool_init(&rnd_global.pool);
LIST_INIT(&rnd_global.sources);
+ cv_init(&rnd_global.cv, "rndsrc");
rnd_mempc = pool_cache_init(sizeof(rnd_sample_t), 0, 0, 0,
"rndsample", NULL, IPL_VM,
@@ -652,6 +671,7 @@ rnd_attach_source(krndsource_t *rs, cons
rs->type = type;
rs->flags = flags;
+ rs->refcnt = 1;
rs->state = rnd_sample_allocate(rs);
@@ -691,6 +711,11 @@ rnd_detach_source(krndsource_t *source)
mutex_spin_enter(&rnd_global.lock);
LIST_REMOVE(source, list);
+ if (0 < --source->refcnt) {
+ do {
+ cv_wait(&rnd_global.cv, &rnd_global.lock);
+ } while (0 < source->refcnt);
+ }
mutex_spin_exit(&rnd_global.lock);
/*
Index: src/sys/sys/rndsource.h
diff -u src/sys/sys/rndsource.h:1.2 src/sys/sys/rndsource.h:1.3
--- src/sys/sys/rndsource.h:1.2 Mon Apr 13 16:02:48 2015
+++ src/sys/sys/rndsource.h Tue Apr 21 03:53:07 2015
@@ -1,4 +1,4 @@
-/* $NetBSD: rndsource.h,v 1.2 2015/04/13 16:02:48 riastradh Exp $ */
+/* $NetBSD: rndsource.h,v 1.3 2015/04/21 03:53:07 riastradh Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -63,6 +63,7 @@ typedef struct krndsource {
void *getarg; /* argument to get-function */
void (*enable)(struct krndsource *, bool); /* turn on/off */
rngtest_t *test; /* test data for RNG type sources */
+ unsigned refcnt;
} krndsource_t;
static inline void
