diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2007-10-16 23:27:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-17 08:42:53 -0700 |
| commit | c17ac85504efec5f3a9b0c5b05bffd6f30e5b655 (patch) | |
| tree | 8643b155ac0530142f2149ddf590ab08bb03b8c2 /kernel/rcutorture.c | |
| parent | b2d9323d139f5c384fa1ef1d74773b4db1c09b3d (diff) | |
Make rcutorture RNG use temporal entropy
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.
[ego@in.ibm.com: Use raw_smp_processor_id() in rcu_random()]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/rcutorture.c')
| -rw-r--r-- | kernel/rcutorture.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index dd413bf6a1d..c3e165c2318 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -41,7 +41,6 @@ #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> @@ -165,16 +164,14 @@ 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(raw_smp_processor_id()); rrsp->rrs_count = RCU_RANDOM_REFRESH; } rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD; |