Module Name: src Committed By: tls Date: Fri Jan 1 16:09:00 UTC 2016
Modified Files: src/sys/kern: kern_rndq.c Log Message: Fix callout-skew source so it runs only when needed (remove second callout, eliminate race). To generate a diff of this commit: cvs rdiff -u -r1.73 -r1.74 src/sys/kern/kern_rndq.c 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:1.73 src/sys/kern/kern_rndq.c:1.74 --- src/sys/kern/kern_rndq.c:1.73 Sat Aug 29 10:00:19 2015 +++ src/sys/kern/kern_rndq.c Fri Jan 1 16:09:00 2016 @@ -1,4 +1,4 @@ -/* $NetBSD: kern_rndq.c,v 1.73 2015/08/29 10:00:19 mlelstv Exp $ */ +/* $NetBSD: kern_rndq.c,v 1.74 2016/01/01 16:09:00 tls 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 1.73 2015/08/29 10:00:19 mlelstv Exp $"); +__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.74 2016/01/01 16:09:00 tls Exp $"); #include <sys/param.h> #include <sys/atomic.h> @@ -407,8 +407,8 @@ rnd_dv_estimate(krndsource_t *rs, uint32 #if defined(__HAVE_CPU_COUNTER) static struct { kmutex_t lock; + int iter; struct callout callout; - struct callout stop_callout; krndsource_t source; } rnd_skew __cacheline_aligned; @@ -426,21 +426,14 @@ rnd_skew_enable(krndsource_t *rs, bool e } static void -rnd_skew_stop_intr(void *arg) -{ - - callout_stop(&rnd_skew.callout); -} - -static void rnd_skew_get(size_t bytes, void *priv) { krndsource_t *skewsrcp = priv; KASSERT(skewsrcp == &rnd_skew.source); if (RND_ENABLED(skewsrcp)) { - /* Measure for 30s */ - callout_schedule(&rnd_skew.stop_callout, hz * 30); + /* Measure 100 times */ + rnd_skew.iter = 100; callout_schedule(&rnd_skew.callout, 1); } } @@ -448,8 +441,6 @@ rnd_skew_get(size_t bytes, void *priv) static void rnd_skew_intr(void *arg) { - static int flipflop; - /* * Even on systems with seemingly stable clocks, the * delta-time entropy estimator seems to think we get 1 bit here @@ -457,14 +448,15 @@ rnd_skew_intr(void *arg) * */ mutex_spin_enter(&rnd_skew.lock); - flipflop = !flipflop; if (RND_ENABLED(&rnd_skew.source)) { - if (flipflop) { + int next_ticks = 1; + if (rnd_skew.iter & 1) { rnd_add_uint32(&rnd_skew.source, rnd_counter()); - callout_schedule(&rnd_skew.callout, hz / 10); - } else { - callout_schedule(&rnd_skew.callout, 1); + next_ticks = hz / 10; + } + if (--rnd_skew.iter > 0) { + callout_schedule(&rnd_skew.callout, next_ticks); } } mutex_spin_exit(&rnd_skew.lock); @@ -559,14 +551,13 @@ rnd_init(void) /* IPL_VM because taken while rnd_global.lock is held. */ mutex_init(&rnd_skew.lock, MUTEX_DEFAULT, IPL_VM); callout_init(&rnd_skew.callout, CALLOUT_MPSAFE); - callout_init(&rnd_skew.stop_callout, CALLOUT_MPSAFE); callout_setfunc(&rnd_skew.callout, rnd_skew_intr, NULL); - callout_setfunc(&rnd_skew.stop_callout, rnd_skew_stop_intr, NULL); rndsource_setcb(&rnd_skew.source, rnd_skew_get, &rnd_skew.source); rndsource_setenable(&rnd_skew.source, rnd_skew_enable); rnd_attach_source(&rnd_skew.source, "callout", RND_TYPE_SKEW, RND_FLAG_COLLECT_VALUE|RND_FLAG_ESTIMATE_VALUE| RND_FLAG_HASCB|RND_FLAG_HASENABLE); + rnd_skew.iter = 100; rnd_skew_intr(NULL); #endif