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| author | Vineet Gupta <vgupta@synopsys.com> | 2016-10-20 07:39:45 -0700 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2016-10-24 09:24:26 -0700 |
| commit | 91e040a79df73d371f70792f30380d4e44805250 (patch) | |
| tree | b2732eadb60fc5575c465a81cc637a899330c1b5 /arch/arc/include/uapi/asm | |
| parent | 1dec78585328db00e33fb18dc1a6deed0e2095a5 (diff) | |
| download | lwn-91e040a79df73d371f70792f30380d4e44805250.tar.gz lwn-91e040a79df73d371f70792f30380d4e44805250.zip | |
ARC: syscall for userspace cmpxchg assist
Older ARC700 cores (ARC750 specifically) lack instructions to implement
atomic r-w-w. This is problematic for userspace libraries such as NPTL
which need atomic primitives. So enable them by providing kernel assist.
This is costly but really the only sane soluton (othern than tight
spinning using the otherwise availiable atomic exchange EX instruciton).
Good thing is there are only a few of these cores running Linux out in
the wild.
This only works on UP systems.
Reviewed-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc/include/uapi/asm')
| -rw-r--r-- | arch/arc/include/uapi/asm/unistd.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/arc/include/uapi/asm/unistd.h b/arch/arc/include/uapi/asm/unistd.h index 41fa2ec9e02c..9a34136d84b2 100644 --- a/arch/arc/include/uapi/asm/unistd.h +++ b/arch/arc/include/uapi/asm/unistd.h @@ -27,18 +27,19 @@ #define NR_syscalls __NR_syscalls +/* Generic syscall (fs/filesystems.c - lost in asm-generic/unistd.h */ +#define __NR_sysfs (__NR_arch_specific_syscall + 3) + /* ARC specific syscall */ #define __NR_cacheflush (__NR_arch_specific_syscall + 0) #define __NR_arc_settls (__NR_arch_specific_syscall + 1) #define __NR_arc_gettls (__NR_arch_specific_syscall + 2) +#define __NR_arc_usr_cmpxchg (__NR_arch_specific_syscall + 4) __SYSCALL(__NR_cacheflush, sys_cacheflush) __SYSCALL(__NR_arc_settls, sys_arc_settls) __SYSCALL(__NR_arc_gettls, sys_arc_gettls) - - -/* Generic syscall (fs/filesystems.c - lost in asm-generic/unistd.h */ -#define __NR_sysfs (__NR_arch_specific_syscall + 3) +__SYSCALL(__NR_arc_usr_cmpxchg, sys_arc_usr_cmpxchg) __SYSCALL(__NR_sysfs, sys_sysfs) #undef __SYSCALL |