Messages in this thread | | | Date | Thu, 24 Jan 2019 20:04:05 +0100 | From | Greg KH <> | Subject | Re: [PATCH stable-4.9.y] locking/qspinlock: Pull in asm/byteorder.h to ensure correct endianness |
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On Thu, Jan 24, 2019 at 06:54:15PM +0000, Will Deacon wrote: > From: Dave Airlie <airlied@redhat.com> > > This commit is not required upstream, but is required for the 4.9.y > stable series. > > Upstream commit 101110f6271c ("Kbuild: always define endianess in > kconfig.h") ensures that either __LITTLE_ENDIAN or __BIG_ENDIAN is > defined to reflect the endianness of the target CPU architecture > regardless of whether or not <asm/byteorder.h> has been #included. The > upstream definition of 'struct qspinlock' relies on this property. > > Unfortunately, the 4.9.y stable series does not provide this guarantee, > so the 'spin_unlock()' routine can erroneously treat the underlying > lockword as big-endian on little-endian architectures using native > qspinlock (i.e. x86_64 without PV) if the caller has not included > <asm/byteorder.h>. This can lead to hangs such as the one in > 'i915_gem_request()' reported via bugzilla: > > https://bugzilla.kernel.org/show_bug.cgi?id=202063 > > Fix the issue by ensuring that <asm/byteorder.h> is #included in > <asm/qspinlock_types.h>, where 'struct qspinlock' is defined.
That is crazy...
Thanks for the patch, now queued up.
greg k-h
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