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| author | Mark Rutland <mark.rutland@arm.com> | 2017-10-24 00:07:21 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-10-25 12:01:02 +0300 |
| commit | 564cbc87937d5de1b5b666b0ed68122d6c74fa07 (patch) | |
| tree | 1e0914440c617c63cbfed989ede9dc90291fa5ca /tools | |
| parent | 94bbc9c1a0b0967509f8ad91323245aad30572f7 (diff) | |
| download | linux-564cbc87937d5de1b5b666b0ed68122d6c74fa07.tar.xz | |
locking/atomics, selftests/powerpc: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.
However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.
The bulk of the kernel code can be transformed via Coccinelle to use
{READ,WRITE}_ONCE(), though this only modifies users of ACCESS_ONCE(),
and not the implementation itself. As such, it has the potential to
break homebrew ACCESS_ONCE() macros seen in some user code in the kernel
tree (e.g. the virtio code, as fixed in commit ea9156fb3b71d9f7).
To avoid fragility if/when that transformation occurs, and to align with
the preferred usage of {READ,WRITE}_ONCE(), this patch updates the DSCR
selftest code to use READ_ONCE() rather than ACCESS_ONCE(). There should
be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-11-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/powerpc/dscr/dscr.h | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/dscr/dscr_default_test.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/tools/testing/selftests/powerpc/dscr/dscr.h b/tools/testing/selftests/powerpc/dscr/dscr.h index 18ea223bd398..cdb840bc54f2 100644 --- a/tools/testing/selftests/powerpc/dscr/dscr.h +++ b/tools/testing/selftests/powerpc/dscr/dscr.h @@ -39,7 +39,7 @@ #define rmb() asm volatile("lwsync":::"memory") #define wmb() asm volatile("lwsync":::"memory") -#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) +#define READ_ONCE(x) (*(volatile typeof(x) *)&(x)) /* Prilvilege state DSCR access */ inline unsigned long get_dscr(void) diff --git a/tools/testing/selftests/powerpc/dscr/dscr_default_test.c b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c index df17c3bab0a7..9e1a37e93b63 100644 --- a/tools/testing/selftests/powerpc/dscr/dscr_default_test.c +++ b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c @@ -27,7 +27,7 @@ static void *do_test(void *in) unsigned long d, cur_dscr, cur_dscr_usr; unsigned long s1, s2; - s1 = ACCESS_ONCE(sequence); + s1 = READ_ONCE(sequence); if (s1 & 1) continue; rmb(); |