From: Andy Grover <andy.grover@oracle.com>
Date: Wed, 24 Mar 2010 00:39:07 +0000 (-0700)
Subject: RDS: Change send lock from a mutex to a spinlock
X-Git-Tag: v2.6.37-rc1~147^2~499^2~64
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=049ee3f500954176a87f22e6ee3e98aecb1b8958;p=pandora-kernel.git

RDS: Change send lock from a mutex to a spinlock

This change allows us to call rds_send_xmit() from a tasklet,
which is crucial to our new operating model.

* Change c_send_lock to a spinlock
* Update stats fields "sem_" to "_lock"
* Remove unneeded rds_conn_is_sending()

About locking between shutdown and send -- send checks if the
connection is up. Shutdown puts the connection into
DISCONNECTING. After this, all threads entering send will exit
immediately. However, a thread could be *in* send_xmit(), so
shutdown acquires the c_send_lock to ensure everyone is out
before proceeding with connection shutdown.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
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