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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-01 13:50:28 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-17 14:59:04 -0700
commitb9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976 (patch)
tree440b7afc650a58987220eb4fffb443552363adf4 /kernel/rcu
parent99a930b0d2b018f31474d69137f311ce3581a4c2 (diff)
downloadlinux-b9a425cfcb3c473b4ca2f3dfaeaf13848f4a7976.tar.bz2
rcu: Pull out wait_event*() condition into helper function
The condition for the wait_event_interruptible_timeout() that waits to do the next force-quiescent-state scan is a bit ornate: ((gf = READ_ONCE(rsp->gp_flags)) & RCU_GP_FLAG_FQS) || (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) This commit therefore pulls this condition out into a helper function and comments its component conditions. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c26
1 files changed, 21 insertions, 5 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4b6594c7db58..b2803730ac13 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1904,6 +1904,26 @@ static int rcu_gp_init(struct rcu_state *rsp)
}
/*
+ * Helper function for wait_event_interruptible_timeout() wakeup
+ * at force-quiescent-state time.
+ */
+static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp)
+{
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ /* Someone like call_rcu() requested a force-quiescent-state scan. */
+ *gfp = READ_ONCE(rsp->gp_flags);
+ if (*gfp & RCU_GP_FLAG_FQS)
+ return true;
+
+ /* The current grace period has completed. */
+ if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
+ return true;
+
+ return false;
+}
+
+/*
* Do one round of quiescent-state forcing.
*/
static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
@@ -2067,11 +2087,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
TPS("fqswait"));
rsp->gp_state = RCU_GP_WAIT_FQS;
ret = wait_event_interruptible_timeout(rsp->gp_wq,
- ((gf = READ_ONCE(rsp->gp_flags)) &
- RCU_GP_FLAG_FQS) ||
- (!READ_ONCE(rnp->qsmask) &&
- !rcu_preempt_blocked_readers_cgp(rnp)),
- j);
+ rcu_gp_fqs_check_wake(rsp, &gf), j);
rsp->gp_state = RCU_GP_DONE_FQS;
/* Locking provides needed memory barriers. */
/* If grace period done, leave loop. */