linux-kernel - [PATCH RESEND 2/3] percpu_ida: Move waking up waiters out of atomic contexts

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Message-Id: <df714a474d1358bf594f3f6dc02cdcf296cef40d.1391688720.git.agordeev@redhat.com>
Date:	Thu,  6 Feb 2014 13:24:54 +0100
From:	Alexander Gordeev <agordeev@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Alexander Gordeev <agordeev@...hat.com>,
	Kent Overstreet <kmo@...erainc.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Jens Axboe <axboe@...nel.dk>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Subject: [PATCH RESEND 2/3] percpu_ida: Move waking up waiters out of atomic contexts

Currently percpu_ida_free() waikes up waiters always with local
interrupts disabled and sometimes with pool->lock held. Yet, it
does not appear there is any reason why it could not be done out
of these atomic contexts.

Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
Cc: Kent Overstreet <kmo@...erainc.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: "Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Acked-by: Kent Overstreet <kmo@...erainc.com>
---
 lib/percpu_ida.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
index fccfb28..c2fa3dc 100644
--- a/lib/percpu_ida.c
+++ b/lib/percpu_ida.c
@@ -229,6 +229,7 @@ void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
 	struct percpu_ida_cpu *tags;
 	unsigned long flags;
 	unsigned nr_free;
+	bool wake_up = false;
 
 	BUG_ON(tag >= pool->nr_tags);
 
@@ -247,7 +248,7 @@ void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
 		 * Pairs with smp_rmb() in steal_tags()
 		 */
 		smp_wmb();
-		wake_up(&pool->wait);
+		wake_up = true;
 	}
 
 	if (nr_free == pool->percpu_max_size) {
@@ -261,13 +262,15 @@ void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
 			move_tags(pool->freelist, &pool->nr_free,
 				  tags->freelist, &tags->nr_free,
 				  pool->percpu_batch_size);
-
-			wake_up(&pool->wait);
+			wake_up = true;
 		}
 		spin_unlock(&pool->lock);
 	}
 
 	local_irq_restore(flags);
+
+	if (wake_up)
+		wake_up(&pool->wait);
 }
 EXPORT_SYMBOL_GPL(percpu_ida_free);
 
-- 
1.7.7.6

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