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From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org, kernel-team@android.com,
	Will Deacon <will@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Segher Boessenkool <segher@kernel.crashing.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Akinobu Mita <akinobu.mita@gmail.com>
Subject: [PATCH v2 03/10] fault_inject: Don't rely on "return value" from WRITE_ONCE()
Date: Thu, 23 Jan 2020 15:33:34 +0000
Message-ID: <20200123153341.19947-4-will@kernel.org> (raw)
In-Reply-To: <20200123153341.19947-1-will@kernel.org>

It's a bit weird that WRITE_ONCE() evaluates to the value it stores and
it's different to smp_store_release(), which can't be used this way.

In preparation for preventing this in WRITE_ONCE(), change the fault
injection code to use a local variable instead.

Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 lib/fault-inject.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 8186ca84910b..ce12621b4275 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -106,7 +106,9 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
 		unsigned int fail_nth = READ_ONCE(current->fail_nth);
 
 		if (fail_nth) {
-			if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
+			fail_nth--;
+			WRITE_ONCE(current->fail_nth, fail_nth);
+			if (!fail_nth)
 				goto fail;
 
 			return false;
-- 
2.25.0.341.g760bfbb309-goog


  parent reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 15:33 [PATCH v2 00/10] Rework READ_ONCE() to improve codegen Will Deacon
2020-01-23 15:33 ` [PATCH v2 01/10] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Will Deacon
2020-01-23 15:33 ` [PATCH v2 02/10] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-01-23 19:07   ` Nick Desaulniers
2020-01-24  8:24     ` Peter Zijlstra
2020-01-24 17:20       ` Nick Desaulniers
2020-01-27 12:04         ` David Laight
2020-01-24 17:36       ` Linus Torvalds
2020-01-24 22:00         ` Peter Zijlstra
2020-01-27 12:21         ` David Laight
2020-01-23 15:33 ` Will Deacon [this message]
2020-01-23 15:33 ` [PATCH v2 04/10] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-01-23 15:33 ` [PATCH v2 05/10] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-01-25  8:27   ` Peter Zijlstra
2020-01-29 10:49     ` Peter Zijlstra
2020-01-23 15:33 ` [PATCH v2 06/10] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-01-23 15:33 ` [PATCH v2 07/10] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-01-23 15:33 ` [PATCH v2 08/10] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-01-23 15:33 ` [PATCH v2 09/10] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8 Will Deacon
2020-01-23 18:36   ` Nick Desaulniers
2020-01-24  8:26     ` Peter Zijlstra
2020-01-24 17:05       ` Nick Desaulniers
2020-01-24 23:29         ` Peter Zijlstra
2020-01-25 10:34         ` Michael Ellerman
2020-01-23 15:33 ` [PATCH v2 10/10] gcov: Remove old GCC 3.4 support Will Deacon
2020-01-23 18:51   ` Nick Desaulniers
2020-01-28 14:56   ` Peter Oberparleiter
2020-01-23 17:07 ` [PATCH v2 00/10] Rework READ_ONCE() to improve codegen David Laight
2020-01-23 17:16   ` Will Deacon
2020-01-23 17:32     ` David Laight
2020-01-23 18:45       ` Nick Desaulniers
2020-01-23 19:01         ` Arvind Sankar
2020-01-24 10:11           ` David Laight
2020-01-26  1:10           ` Qais Yousef
2020-01-27  7:26             ` Arnd Bergmann
2020-01-23 17:59 ` Linus Torvalds
2020-01-24  8:33   ` Peter Zijlstra
2020-01-24 10:41     ` Peter Zijlstra
2020-02-10  9:50     ` Masahiro Yamada
2020-02-10  9:59       ` Will Deacon
2020-01-31 10:20 ` David Howells

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