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This was previously implemented using a cmpxchg() loop. Replace the cmpxchg() loop with a single xchg(), which provides the same atomic get-and-clear semantics, avoids retry spinning under contention, and simplifies the code. The code on x86_64 improves from: 186: 8b 15 00 00 00 00 mov 0x0(%rip),%edx 18c: 89 d0 mov %edx,%eax 18e: f0 0f b1 0d 00 00 00 lock cmpxchg %ecx,0x0(%rip) 195: 00 196: 39 c2 cmp %eax,%edx 198: 75 ec jne 186 <...> to just: 186: 87 05 00 00 00 00 xchg %eax,0x0(%rip) No functional change intended. Signed-off-by: Uros Bizjak Cc: Juergen Gross Cc: Stefano Stabellini Cc: Oleksandr Tyshchenko --- drivers/xen/mcelog.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c index 4f65b641c054..abe658c73b7b 100644 --- a/drivers/xen/mcelog.c +++ b/drivers/xen/mcelog.c @@ -165,9 +165,7 @@ static long xen_mce_chrdev_ioctl(struct file *f, unsigned int cmd, case MCE_GETCLEAR_FLAGS: { unsigned flags; - do { - flags = xen_mcelog.flags; - } while (cmpxchg(&xen_mcelog.flags, flags, 0) != flags); + flags = xchg(&xen_mcelog.flags, 0); return put_user(flags, p); } -- 2.52.0