Messages in this thread | | | Date | Tue, 14 Jan 2014 13:13:33 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] hvc: ensure hvc_init is only ever called once in hvc_console.c |
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On Tue, Jan 14, 2014 at 04:03:37PM -0500, Paul Gortmaker wrote: > 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: stable@vger.kernel.org # v2.6.24+ > Cc: Rusty Russell <rusty@rustcorp.com.au> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Fixes: 3e6c6f630a52 ("Delay creation of khcvd thread") > Reported-by: Jim Somerville <Jim.Somerville@windriver.com> > Tested-by: Jim Somerville <Jim.Somerville@windriver.com> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> > --- > > [Greg: I realize tty-next is closed; given that this is an ancient > bug, I don't see any real urgency here, so feel free to queue it > whenever/whereever is most convenient - assuming it is an OK fix.]
Looks ok, I'll queue it up after 3.14-rc1 is out, thanks.
greg k-h
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