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author | Pavel Kozlov <pavel.kozlov@synopsys.com> | 2023-08-15 18:11:36 +0300 |
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committer | Vineet Gupta <vgupta@kernel.org> | 2023-08-16 03:27:26 +0300 |
commit | 42f51fb24fd39cc547c086ab3d8a314cc603a91c (patch) | |
tree | 296dcde00f8246e66920889547795d8a4a91db91 /arch/arc/include/asm/uaccess.h | |
parent | 4d3696801bad2a037832c15a8d21dfe0c529d9cd (diff) | |
download | linux-42f51fb24fd39cc547c086ab3d8a314cc603a91c.tar.xz |
ARC: atomics: Add compiler barrier to atomic operations...
... to avoid unwanted gcc optimizations
SMP kernels fail to boot with commit 596ff4a09b89
("cpumask: re-introduce constant-sized cpumask optimizations").
|
| percpu: BUG: failure at mm/percpu.c:2981/pcpu_build_alloc_info()!
|
The write operation performed by the SCOND instruction in the atomic
inline asm code is not properly passed to the compiler. The compiler
cannot correctly optimize a nested loop that runs through the cpumask
in the pcpu_build_alloc_info() function.
Fix this by add a compiler barrier (memory clobber in inline asm).
Apparently atomic ops used to have memory clobber implicitly via
surrounding smp_mb(). However commit b64be6836993c431e
("ARC: atomics: implement relaxed variants") removed the smp_mb() for
the relaxed variants, but failed to add the explicit compiler barrier.
Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/135
Cc: <stable@vger.kernel.org> # v6.3+
Fixes: b64be6836993c43 ("ARC: atomics: implement relaxed variants")
Signed-off-by: Pavel Kozlov <pavel.kozlov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@kernel.org>
[vgupta: tweaked the changelog and added Fixes tag]
Diffstat (limited to 'arch/arc/include/asm/uaccess.h')
0 files changed, 0 insertions, 0 deletions