drawterm/libc/lock.c

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#include <u.h>
#include <libc.h>
int
canlock(Lock *lk)
{
return !tas(&lk->key);
}
void
lock(Lock *lk)
{
int i;
/* easy case */
if(canlock(lk))
return;
/* for multi processor machines */
for(i=0; i<100; i++)
if(canlock(lk))
return;
for(i=0; i<100; i++) {
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osyield();
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if(canlock(lk))
return;
}
/* looking bad - make sure it is not a priority problem */
for(i=0; i<12; i++) {
osmsleep(1<<i);
if(canlock(lk))
return;
}
/* we are in trouble */
for(;;) {
if(canlock(lk))
return;
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iprint("lock loop %ld: val=%d &lock=%ux pc=%p\n", getpid(), lk->key, lk, getcallerpc(&lk));
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osmsleep(1000);
}
}
void
unlock(Lock *lk)
{
assert(lk->key);
lk->key = 0;
}
void
ilock(Lock *lk)
{
lock(lk);
}
void
iunlock(Lock *lk)
{
unlock(lk);
}