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author | iap10@labyrinth.cl.cam.ac.uk <iap10@labyrinth.cl.cam.ac.uk> | 2003-02-24 16:55:07 +0000 |
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committer | iap10@labyrinth.cl.cam.ac.uk <iap10@labyrinth.cl.cam.ac.uk> | 2003-02-24 16:55:07 +0000 |
commit | a48212cb65e09669ed243581556529681cebba0a (patch) | |
tree | a58f47e4764f343db87eba48d17ce9b2ddbf8047 /xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c | |
parent | 96ce9e11d148a721557d48ed5a8ca7857a7bc937 (diff) | |
download | xen-a48212cb65e09669ed243581556529681cebba0a.tar.gz xen-a48212cb65e09669ed243581556529681cebba0a.tar.bz2 xen-a48212cb65e09669ed243581556529681cebba0a.zip |
bitkeeper revision 1.93 (3e5a4e6bkPheUp3x1uufN2MS3LAB7A)
Latest and Greatest version of XenoLinux based on the Linux-2.4.21-pre4
kernel.
Diffstat (limited to 'xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c')
-rw-r--r-- | xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c b/xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c new file mode 100644 index 0000000000..ffd4869001 --- /dev/null +++ b/xenolinux-2.4.21-pre4-sparse/arch/xeno/lib/dec_and_lock.c @@ -0,0 +1,40 @@ +/* + * x86 version of "atomic_dec_and_lock()" using + * the atomic "cmpxchg" instruction. + * + * (For CPU's lacking cmpxchg, we use the slow + * generic version, and this one never even gets + * compiled). + */ + +#include <linux/spinlock.h> +#include <asm/atomic.h> + +int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) +{ + int counter; + int newcount; + +repeat: + counter = atomic_read(atomic); + newcount = counter-1; + + if (!newcount) + goto slow_path; + + asm volatile("lock; cmpxchgl %1,%2" + :"=a" (newcount) + :"r" (newcount), "m" (atomic->counter), "0" (counter)); + + /* If the above failed, "eax" will have changed */ + if (newcount != counter) + goto repeat; + return 0; + +slow_path: + spin_lock(lock); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock(lock); + return 0; +} |