linux-kernel - [PATCH] dma-debug: Avoid spinlock recursion when disabling dma-debug

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Message-Id: <1463678421-18683-1-git-send-email-ville.syrjala@linux.intel.com>
Date:	Thu, 19 May 2016 20:20:21 +0300
From:	ville.syrjala@...ux.intel.com
To:	linux-kernel@...r.kernel.org
Cc:	stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>
Subject: [PATCH] dma-debug: Avoid spinlock recursion when disabling dma-debug

From: Ville Syrjälä <ville.syrjala@...ux.intel.com>

With netconsole (at least) the pr_err("... disabling\n") call
can recurse back into the dma-debug code, where it'll try to
grab free_entries_lock again. Avoid the problem by doing
the printk after dropping the lock.

Cc: stable@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
---
 lib/dma-debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 4a1515f4b452..51a76af25c66 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -657,9 +657,9 @@ static struct dma_debug_entry *dma_entry_alloc(void)
 	spin_lock_irqsave(&free_entries_lock, flags);
 
 	if (list_empty(&free_entries)) {
-		pr_err("DMA-API: debugging out of memory - disabling\n");
 		global_disable = true;
 		spin_unlock_irqrestore(&free_entries_lock, flags);
+		pr_err("DMA-API: debugging out of memory - disabling\n");
 		return NULL;
 	}
 
-- 
2.7.4