linux-kernel - [PATCH] dma-debug: release free_entries

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Date:	Wed,  4 Apr 2012 03:19:10 +0200
From:	Jakub Kicinski <kubakici@...pl>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	linux-kernel@...r.kernel.org, Jakub Kicinski <kubakici@...pl>
Subject: [PATCH] dma-debug: release free_entries_lock before saving stack trace

Saving stack trace can take a while and once the entry
is allocated free_entries_lock is no longer needed.

Signed-off-by: Jakub Kicinski <kubakici@...pl>
---
This gives me 20-25% increase in throughput of Ethernet NIC
on system with Intel Atom DN2800.
---
 lib/dma-debug.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index fea790a..2567755 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -431,7 +431,7 @@ static struct dma_debug_entry *__dma_entry_alloc(void)
  */
 static struct dma_debug_entry *dma_entry_alloc(void)
 {
-	struct dma_debug_entry *entry = NULL;
+	struct dma_debug_entry *entry;
 	unsigned long flags;
 
 	spin_lock_irqsave(&free_entries_lock, flags);
@@ -439,11 +439,14 @@ static struct dma_debug_entry *dma_entry_alloc(void)
 	if (list_empty(&free_entries)) {
 		pr_err("DMA-API: debugging out of memory - disabling\n");
 		global_disable = true;
-		goto out;
+		spin_unlock_irqrestore(&free_entries_lock, flags);
+		return NULL;
 	}
 
 	entry = __dma_entry_alloc();
 
+	spin_unlock_irqrestore(&free_entries_lock, flags);
+
 #ifdef CONFIG_STACKTRACE
 	entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
 	entry->stacktrace.entries = entry->st_entries;
@@ -451,9 +454,6 @@ static struct dma_debug_entry *dma_entry_alloc(void)
 	save_stack_trace(&entry->stacktrace);
 #endif
 
-out:
-	spin_unlock_irqrestore(&free_entries_lock, flags);
-
 	return entry;
 }
 
-- 
1.7.7.6

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