netdev - [PATCH net RFC 1/2] netdevice: add might_sleep() call to napi

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Date:	Wed, 18 Sep 2013 13:20:10 -0700
From:	Jacob Keller <jacob.e.keller@...el.com>
To:	netdev@...r.kernel.org
Cc:	Alex Duyck <alexander.h.duyck@...el.com>,
	Hyong-Youb Kim <hykim@...i.com>,
	Dmitry Kravkov <dmitry@...adcom.com>,
	Amir Vadai <amirv@...lanox.com>,
	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Subject: [PATCH net RFC 1/2] netdevice: add might_sleep() call to
 napi_disable

napi_disable potentially calls msleep(1) if the NAPI_STATE_SCHED bit is
previously set by something else. Because it does not always call msleep, it
was difficult to track down a bug related to calling napi_disable within
local_bh_disable()d context. This patch adds a might_sleep() call to the
napi_disable routine in order to aid in the future debugging of similar issues.
This will cause a BUG in drivers which have implemented busy polling in a
similar fashion to ixgbe, and which call napi_disable inside the
local_bh_disable()d section where the vector napi lock is taken.

Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
Cc: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Cc: Alex Duyck <alexander.h.duyck@...el.com>
Cc: Hyong-Youb Kim <hykim@...i.com>
Cc: Amir Vadai <amirv@...lanox.com>
Cc: Dmitry Kravkov <dmitry@...adcom.com>
---
 include/linux/netdevice.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3de49ac..81dab00 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -483,6 +483,8 @@ extern void napi_hash_del(struct napi_struct *napi);
  */
 static inline void napi_disable(struct napi_struct *n)
 {
+	might_sleep();
+
 	set_bit(NAPI_STATE_DISABLE, &n->state);
 	while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
 		msleep(1);

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