[src/trunk]: src/sys/rump/librump/rumpkern Revert previous -- a little too qu...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f76ce6330381
branches:  trunk
changeset: 337609:f76ce6330381
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Apr 21 04:05:57 2015 +0000

description:
Revert previous -- a little too quick on the commit trigger.

Ran some tests but not enough.  There is a deadlock against myself:

rndsink_request acquires rndsinks_lock
-> rnd_getmore
-> hyperentropy feedrandom (or any other rndsource callback)
-> rnd_add_data
-> rndsinks_distribute acquires rndsinks_lock

Need to break this cycle before rndsource callbacks can invoke
rnd_add_data.

diffstat:

 sys/rump/librump/rumpkern/hyperentropy.c |  46 +++++++++++++++++++++++++++----
 1 files changed, 40 insertions(+), 6 deletions(-)

diffs (81 lines):

diff -r 907f90f1200e -r f76ce6330381 sys/rump/librump/rumpkern/hyperentropy.c
--- a/sys/rump/librump/rumpkern/hyperentropy.c  Tue Apr 21 03:53:50 2015 +0000
+++ b/sys/rump/librump/rumpkern/hyperentropy.c  Tue Apr 21 04:05:57 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: hyperentropy.c,v 1.9 2015/04/21 03:53:50 riastradh Exp $       */
+/*     $NetBSD: hyperentropy.c,v 1.10 2015/04/21 04:05:57 riastradh Exp $      */
 
 /*
  * Copyright (c) 2014 Antti Kantee.  All Rights Reserved.
@@ -26,9 +26,10 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: hyperentropy.c,v 1.9 2015/04/21 03:53:50 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: hyperentropy.c,v 1.10 2015/04/21 04:05:57 riastradh Exp $");
 
 #include <sys/param.h>
+#include <sys/atomic.h>
 #include <sys/kmem.h>
 #include <sys/rndpool.h>
 #include <sys/rndsource.h>
@@ -38,10 +39,12 @@
 #include "rump_private.h"
 
 static krndsource_t rndsrc;
+static volatile unsigned hyperentropy_wanted;
+static void *feedrandom_softint;
 
 #define MAXGET (RND_POOLBITS/NBBY)
 static void
-feedrandom_cb(size_t bytes, void *cookie __unused)
+feedrandom(size_t bytes)
 {
        uint8_t *rnddata;
        size_t dsize;
@@ -53,11 +56,42 @@
        kmem_intr_free(rnddata, MAXGET);
 }
 
+static void
+feedrandom_intr(void *cookie __unused)
+{
+
+       feedrandom(atomic_swap_uint(&hyperentropy_wanted, 0));
+}
+
+static void
+feedrandom_cb(size_t bytes, void *cookie __unused)
+{
+       unsigned old, new;
+
+       do {
+               old = hyperentropy_wanted;
+               new = ((MAXGET - old) < bytes? MAXGET : (old + bytes));
+       } while (atomic_cas_uint(&hyperentropy_wanted, old, new) != old);
+
+       softint_schedule(feedrandom_softint);
+}
+
 void
 rump_hyperentropy_init(void)
 {
 
-       rndsource_setcb(&rndsrc, &feedrandom_cb, &rndsrc);
-       rnd_attach_source(&rndsrc, "rump_hyperent", RND_TYPE_VM,
-           RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
+       if (rump_threads) {
+               feedrandom_softint =
+                   softint_establish(SOFTINT_CLOCK|SOFTINT_MPSAFE,
+                       feedrandom_intr, NULL);
+               KASSERT(feedrandom_softint != NULL);
+               rndsource_setcb(&rndsrc, feedrandom_cb, &rndsrc);
+               rnd_attach_source(&rndsrc, "rump_hyperent", RND_TYPE_VM,
+                   RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
+       } else {
+               /* without threads, just fill the pool */
+               rnd_attach_source(&rndsrc, "rump_hyperent", RND_TYPE_VM,
+                   RND_FLAG_COLLECT_VALUE);
+               feedrandom(MAXGET);
+       }
 }