Mikulas Patocka c81e34c434 alpha: fix memory barriers so that they conform to the specification ... commit 54505a1e20 upstream. The commits cd0e00c106 and 92d7223a74 broke boot on the Alpha Avanti platform. The patches move memory barriers after a write before the write. The result is that if there's iowrite followed by ioread, there is no barrier between them. The Alpha architecture allows reordering of the accesses to the I/O space, and the missing barrier between write and read causes hang with serial port and real time clock. This patch makes barriers confiorm to the specification. 1. We add mb() before readX_relaxed and writeX_relaxed - memory-barriers.txt claims that these functions must be ordered w.r.t. each other. Alpha doesn't order them, so we need an explicit barrier. 2. We add mb() before reads from the I/O space - so that if there's a write followed by a read, there should be a barrier between them. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Fixes: cd0e00c106 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering") Fixes: 92d7223a74 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2") Cc: stable@vger.kernel.org # v4.17+ Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Reviewed-by: Maciej W. Rozycki <macro@linux-mips.org> Signed-off-by: Matt Turner <mattst88@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-06-22 09:31:21 +02:00
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boot	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152	2019-05-30 11:26:32 -07:00
configs	alpha: move arch/alpha/defconfig to arch/alpha/configs/defconfig	2019-05-18 11:49:55 +09:00
include	alpha: fix memory barriers so that they conform to the specification	2020-06-22 09:31:21 +02:00
kernel	alpha: fix memory barriers so that they conform to the specification	2020-06-22 09:31:21 +02:00
lib	Remove 'type' argument from access_ok() function	2019-01-03 18:57:57 -08:00
math-emu	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
mm	Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2019-07-08 21:48:15 -07:00
oprofile	smp: Remove smp_call_function() and on_each_cpu() return values	2019-06-23 14:26:26 +02:00
Kconfig	kbuild: add CONFIG_ASM_MODVERSIONS	2019-08-22 01:14:11 +09:00
Kconfig.debug	Kconfig: consolidate the "Kernel hacking" menu	2018-08-02 08:06:48 +09:00
Makefile	kconfig: make arch/*/configs/defconfig the default of KBUILD_DEFCONFIG	2019-06-09 15:08:18 +09:00