linux-kernel - [PATCH 1/3] sched: enable interrupts and drop rq-lock during newidle balancing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080623230440.31515.97377.stgit@lsg.lsg.lab.novell.com>
Date:	Mon, 23 Jun 2008 17:04:40 -0600
From:	Gregory Haskins <ghaskins@...ell.com>
To:	mingo@...e.hu, rostedt@...dmis.org, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	linux-rt-users@...r.kernel.org, ghaskins@...ell.com,
	dbahi@...ell.com
Subject: [PATCH 1/3] sched: enable interrupts and drop rq-lock during newidle
	balancing

We do find_busiest_groups() et. al. without locks held for normal balancing,
so lets do it for newidle as well.  It will allow other cpus to make
forward progress (against our RQ) while we try to balance and allow 
some interrupts to occur.

Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
---

 kernel/sched.c |   44 ++++++++++++++++++++++++++++++++++++++------
 1 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 31f91d9..490e6bc 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3333,6 +3333,16 @@ load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
 	int sd_idle = 0;
 	int all_pinned = 0;
 	cpumask_t cpus = CPU_MASK_ALL;
+	int nr_running;
+
+	schedstat_inc(sd, lb_count[CPU_NEWLY_IDLE]);
+
+	/*
+	 * We are in a preempt-disabled section, so dropping the lock/irq
+	 * here simply means that other cores may acquire the lock,
+	 * and interrupts may occur.
+	 */
+	spin_unlock_irq(&this_rq->lock);
 
 	/*
 	 * When power savings policy is enabled for the parent domain, idle
@@ -3344,7 +3354,6 @@ load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
 	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
 		sd_idle = 1;
 
-	schedstat_inc(sd, lb_count[CPU_NEWLY_IDLE]);
 redo:
 	group = find_busiest_group(sd, this_cpu, &imbalance, CPU_NEWLY_IDLE,
 				   &sd_idle, &cpus, NULL);
@@ -3366,14 +3375,33 @@ redo:
 
 	ld_moved = 0;
 	if (busiest->nr_running > 1) {
-		/* Attempt to move tasks */
-		double_lock_balance(this_rq, busiest);
-		/* this_rq->clock is already updated */
-		update_rq_clock(busiest);
+		local_irq_disable();
+		double_rq_lock(this_rq, busiest);
+
+		BUG_ON(this_cpu != smp_processor_id());
+
+		/*
+		 * Checking rq->nr_running covers both the case where
+		 * newidle-balancing pulls a task, as well as if something
+		 * else issued a NEEDS_RESCHED (since we would only need
+		 * a reschedule if something was moved to us)
+		 */
+		if (this_rq->nr_running) {
+			double_rq_unlock(this_rq, busiest);
+			local_irq_enable();
+			goto out_balanced;
+		}
+
 		ld_moved = move_tasks(this_rq, this_cpu, busiest,
 					imbalance, sd, CPU_NEWLY_IDLE,
 					&all_pinned);
-		spin_unlock(&busiest->lock);
+
+		nr_running = this_rq->nr_running;
+		double_rq_unlock(this_rq, busiest);
+		local_irq_enable();
+
+		if (nr_running)
+			goto out_balanced;
 
 		if (unlikely(all_pinned)) {
 			cpu_clear(cpu_of(busiest), cpus);
@@ -3382,6 +3410,8 @@ redo:
 		}
 	}
 
+	spin_lock_irq(&this_rq->lock);
+
 	if (!ld_moved) {
 		schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]);
 		if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
@@ -3393,6 +3423,8 @@ redo:
 	return ld_moved;
 
 out_balanced:
+	spin_lock_irq(&this_rq->lock);
+
 	schedstat_inc(sd, lb_balanced[CPU_NEWLY_IDLE]);
 	if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
 	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/