The patch titled
Make rcutorture RNG use temporal entropy
has been added to the -mm tree. Its filename is
make-rcutorture-rng-use-temporal-entropy.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Make rcutorture RNG use temporal entropy
From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Repost of http://lkml.org/lkml/2007/8/10/472 made available by request.
The locking used by get_random_bytes() can conflict with the
preempt_disable() and synchronize_sched() form of RCU. This patch changes
rcutorture's RNG to gather entropy from the new cpu_clock() interface
(relying on interrupts, preemption, daemons, and rcutorture's reader
thread's rock-bottom scheduling priority to provide useful entropy), and
also adds and EXPORT_SYMBOL_GPL() to make that interface available to GPLed
kernel modules such as rcutorture.
Passes several hours of rcutorture.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/rcutorture.c | 8 ++------
kernel/sched.c | 2 ++
2 files changed, 4 insertions(+), 6 deletions(-)
diff -puN kernel/rcutorture.c~make-rcutorture-rng-use-temporal-entropy kernel/rcutorture.c
--- a/kernel/rcutorture.c~make-rcutorture-rng-use-temporal-entropy
+++ a/kernel/rcutorture.c
@@ -42,7 +42,6 @@
#include <linux/notifier.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
-#include <linux/random.h>
#include <linux/delay.h>
#include <linux/byteorder/swabb.h>
#include <linux/stat.h>
@@ -166,16 +165,13 @@ struct rcu_random_state {
/*
* Crude but fast random-number generator. Uses a linear congruential
- * generator, with occasional help from get_random_bytes().
+ * generator, with occasional help from cpu_clock().
*/
static unsigned long
rcu_random(struct rcu_random_state *rrsp)
{
- long refresh;
-
if (--rrsp->rrs_count < 0) {
- get_random_bytes(&refresh, sizeof(refresh));
- rrsp->rrs_state += refresh;
+ rrsp->rrs_state += (unsigned long)cpu_clock(smp_processor_id());
rrsp->rrs_count = RCU_RANDOM_REFRESH;
}
rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
diff -puN kernel/sched.c~make-rcutorture-rng-use-temporal-entropy kernel/sched.c
--- a/kernel/sched.c~make-rcutorture-rng-use-temporal-entropy
+++ a/kernel/sched.c
@@ -399,6 +399,8 @@ unsigned long long cpu_clock(int cpu)
return now;
}
+EXPORT_SYMBOL_GPL(cpu_clock);
+
#ifdef CONFIG_FAIR_GROUP_SCHED
/* Change a task's ->cfs_rq if it moves across CPUs */
static inline void set_task_cfs_rq(struct task_struct *p)
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxxxxxxxxxx are
immunize-rcu_dereference-against-crazy-compiler-writers.patch
remove-workaround-for-unimmunized-rcu_dereference-from-mce_log.patch
clean-up-duplicate-includes-in-kernel.patch
make-rcutorture-rng-use-temporal-entropy.patch
make-access-to-tasks-nsproxy-lighter.patch
-
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