The patch titled
Allow rcutorture to handle synchronize_sched()
has been removed from the -mm tree. Its filename was
allow-rcutorture-to-handle-synchronize_sched.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
Subject: Allow rcutorture to handle synchronize_sched()
From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
The rcutorture module uses a random-number generator that periodically
calls get_random_bytes() to add entropy. This random-number generator is
invoked from within the RCU read-side critical section, which, in the case
of the synchronize_sched() variant of RCU, has preeemption disabled.
Unfortunately, get_random_bytes() ends up acquiring normal spinlocks, which
can block in -rt, resulting in very large numbers of "scheduling while
atomic" messages.
This patch takes a very crude approach, simply substituting the time
of day for get_random_bytes().
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Josh Triplett <josh@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/rcutorture.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff -puN kernel/rcutorture.c~allow-rcutorture-to-handle-synchronize_sched kernel/rcutorture.c
--- a/kernel/rcutorture.c~allow-rcutorture-to-handle-synchronize_sched
+++ a/kernel/rcutorture.c
@@ -166,16 +166,13 @@ 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 the time-of-day 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 += xtime.tv_nsec;
rrsp->rrs_count = RCU_RANDOM_REFRESH;
}
rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxxxxxxxxxx are
allow-rcutorture-to-handle-synchronize_sched.patch
rcu-remove-prototype-for-nonexistent-function.patch
fib_trie-cleanup-fix.patch
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-access-to-tasks-nsproxy-lighter.patch
-
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