From: Paul Gortmaker Date: Tue, 14 Jan 2014 21:03:37 +0000 (-0500) Subject: hvc: ensure hvc_init is only ever called once in hvc_console.c X-Git-Tag: v3.2.58~65 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d666ac7d1b5a09b7d148850289c8abaf3c3aa215;p=pandora-kernel.git hvc: ensure hvc_init is only ever called once in hvc_console.c commit f76a1cbed18c86e2d192455f0daebb48458965f3 upstream. Commit 3e6c6f630a5282df8f3393a59f10eb9c56536d23 ("Delay creation of khcvd thread") moved the call of hvc_init from being a device_initcall into hvc_alloc, and used a non-null hvc_driver as indication of whether hvc_init had already been called. The problem with this is that hvc_driver is only assigned a value at the bottom of hvc_init, and so there is a window where multiple hvc_alloc calls can be in progress at the same time and hence try and call hvc_init multiple times. Previously the use of device_init guaranteed that hvc_init was only called once. This manifests itself as sporadic instances of two hvc_init calls racing each other, and with the loser of the race getting -EBUSY from tty_register_driver() and hence that virtual console fails: Couldn't register hvc console driver virtio-ports vport0p1: error -16 allocating hvc for port Here we add an atomic_t to guarantee we'll never run hvc_init twice. Cc: Rusty Russell Cc: Greg Kroah-Hartman Fixes: 3e6c6f630a52 ("Delay creation of khcvd thread") Reported-by: Jim Somerville Tested-by: Jim Somerville Signed-off-by: Paul Gortmaker Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed