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[PATCH 3.16 124/305] dma-debug: avoid spinlock recursion when disabling dma-debug

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  [PATCH 3.16 124/305] dma-debug: avoid spinlock recursion when  disabling dma-debug Ben Hutchings <ben@decadent.org.uk> - 2016-08-14 13:10 +0200

#1461824 — [PATCH 3.16 124/305] dma-debug: avoid spinlock recursion when disabling dma-debug

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 3017cd63f26fc655d56875aaf497153ba60e9edf upstream.

With netconsole (at least) the pr_err("...  disablingn") 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.

Link: http://lkml.kernel.org/r/1463678421-18683-1-git-send-email-ville.syrjala@linux.intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 lib/dma-debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -646,9 +646,9 @@ static struct dma_debug_entry *dma_entry
 	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;
 	}
 

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