diff options
Diffstat (limited to 'src/lib9/lock.c')
-rw-r--r-- | src/lib9/lock.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/src/lib9/lock.c b/src/lib9/lock.c new file mode 100644 index 00000000..2da73626 --- /dev/null +++ b/src/lib9/lock.c @@ -0,0 +1,54 @@ +#include <unistd.h> +#include <sched.h> +#include <lib9.h> + +int _ntas; +static int +_xtas(void *v) +{ + int x; + +_ntas++; + x = _tas(v); + if(x == 0 || x == 0xCAFEBABE) + return x; + fprint(2, "%d: tas %p got %ux\n", getpid(), v, x); + abort(); +} + +int +canlock(Lock *l) +{ + return !_xtas(&l->val); +} + +void +unlock(Lock *l) +{ + l->val = 0; +} + +void +lock(Lock *lk) +{ + int i; + + /* once fast */ + if(!_xtas(&lk->val)) + return; + /* a thousand times pretty fast */ + for(i=0; i<1000; i++){ + if(!_xtas(&lk->val)) + return; + sched_yield(); + } + /* now nice and slow */ + for(i=0; i<1000; i++){ + if(!_xtas(&lk->val)) + return; + usleep(100*1000); + } + /* take your time */ + while(_xtas(&lk->val)) + usleep(1000*1000); +} |