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| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-05-18 13:52:44 -0700 |
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| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-05-18 13:52:44 -0700 |
| commit | 936a0cd52aa5d024c583e36e2f21bf6ec2e527e4 (patch) | |
| tree | 01cffc11361be7d671b71ba86463f6649b39d552 /include/linux/compiler-gcc.h | |
| parent | 36bf51acc89d113f101e40f40af4ab53fbf5b60a (diff) | |
| parent | e26081808edadfd257c6c9d81014e3b25e9a6118 (diff) | |
| download | lwn-936a0cd52aa5d024c583e36e2f21bf6ec2e527e4.tar.gz lwn-936a0cd52aa5d024c583e36e2f21bf6ec2e527e4.zip | |
Merge 4.1-rc4 into staging-next
We want the fixes in here for testing and merge issues.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/compiler-gcc.h')
| -rw-r--r-- | include/linux/compiler-gcc.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index cdf13ca7cac3..371e560d13cf 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -9,10 +9,24 @@ + __GNUC_MINOR__ * 100 \ + __GNUC_PATCHLEVEL__) - /* Optimization barrier */ + /* The "volatile" is due to gcc bugs */ #define barrier() __asm__ __volatile__("": : :"memory") +/* + * This version is i.e. to prevent dead stores elimination on @ptr + * where gcc and llvm may behave differently when otherwise using + * normal barrier(): while gcc behavior gets along with a normal + * barrier(), llvm needs an explicit input variable to be assumed + * clobbered. The issue is as follows: while the inline asm might + * access any memory it wants, the compiler could have fit all of + * @ptr into memory registers instead, and since @ptr never escaped + * from that, it proofed that the inline asm wasn't touching any of + * it. This version works well with both compilers, i.e. we're telling + * the compiler that the inline asm absolutely may see the contents + * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 + */ +#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") /* * This macro obfuscates arithmetic on a variable address so that gcc |