[PATCH] firewire: core: reduce stack usage in bus reset tasklet

[PATCH] firewire: core: reduce stack usage in bus reset tasklet

[Stefan Richter]

fw_compute_block_crc() used 1024 bytes of the kernel stack.  This
function is called
  - in process context when the local node's config ROM is updated,
  - in tasklet context of the bus reset handler.

Replace the stack-allocated buffer by a static buffer.
Serialize buffer accesses by a static local spinlock.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
 drivers/firewire/core-card.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Index: linux-2.6.31-rc8/drivers/firewire/core-card.c
===================================================================
--- linux-2.6.31-rc8.orig/drivers/firewire/core-card.c
+++ linux-2.6.31-rc8/drivers/firewire/core-card.c
@@ -40,13 +40,19 @@
 
 int fw_compute_block_crc(u32 *block)
 {
-	__be32 be32_block[256];
+	static DEFINE_SPINLOCK(buffer_lock);
+	static __be32 buffer[256];
+	unsigned long flags;
 	int i, length;
 
+	spin_lock_irqsave(&buffer_lock, flags);
+
 	length = (*block >> 16) & 0xff;
 	for (i = 0; i < length; i++)
-		be32_block[i] = cpu_to_be32(block[i + 1]);
-	*block |= crc_itu_t(0, (u8 *) be32_block, length * 4);
+		buffer[i] = cpu_to_be32(block[i + 1]);
+	*block |= crc_itu_t(0, (u8 *)buffer, length * 4);
+
+	spin_unlock_irqrestore(&buffer_lock, flags);
 
 	return length;
 }

-- 
Stefan Richter
-=====-==--= =--- ===--
http://arcgraph.de/sr/