runtime·stackalloc(uint32 n)
{
uint32 pos;
void *v;
// Stackalloc must be called on scheduler stack, so that we
// never try to grow the stack during the code that stackalloc runs.
// Doing so would cause a deadlock (issue 1547).
if(g != m->g0)
runtime·throw("stackalloc not on scheduler stack");
// Stack allocator uses malloc/free most of the time,
// but if we're in the middle of malloc and need stack,
// we have to do something else to avoid deadlock.
// In that case, we fall back on a fixed-size free-list
// allocator, assuming that inside malloc all the stack
// frames are small, so that all the stack allocations
// will be a single size, the minimum (right now, 5k).
if(n == FixedStack || m->mallocing || m->gcing) {
if(n != FixedStack) {
runtime·printf("stackalloc: in malloc, size=%d want %d\n", FixedStack, n);
runtime·throw("stackalloc");
}
if(m->stackcachecnt == 0)
stackcacherefill();
pos = m->stackcachepos;
pos = (pos - 1) % StackCacheSize;
v = m->stackcache[pos];
m->stackcachepos = pos;
m->stackcachecnt--;
m->stackinuse++;
return v;
}
return runtime·mallocgc(n, FlagNoProfiling|FlagNoGC, 0, 0);
}
runtime·stackalloc(G *gp, uint32 n)
{
uint32 pos;
void *v;
bool malloced;
Stktop *top;
// Stackalloc must be called on scheduler stack, so that we
// never try to grow the stack during the code that stackalloc runs.
// Doing so would cause a deadlock (issue 1547).
if(g != m->g0)
runtime·throw("stackalloc not on scheduler stack");
if((n & (n-1)) != 0)
runtime·throw("stack size not a power of 2");
if(StackDebug >= 1)
runtime·printf("stackalloc %d\n", n);
gp->stacksize += n;
if(runtime·debug.efence || StackFromSystem) {
v = runtime·SysAlloc(ROUND(n, PageSize), &mstats.stacks_sys);
if(v == nil)
runtime·throw("out of memory (stackalloc)");
return v;
}
// Minimum-sized stacks are allocated with a fixed-size free-list allocator,
// but if we need a stack of a bigger size, we fall back on malloc
// (assuming that inside malloc all the stack frames are small,
// so that we do not deadlock).
malloced = true;
if(n == FixedStack || m->mallocing) {
if(n != FixedStack) {
runtime·printf("stackalloc: in malloc, size=%d want %d\n", FixedStack, n);
runtime·throw("stackalloc");
}
if(m->stackcachecnt == 0)
stackcacherefill();
pos = m->stackcachepos;
pos = (pos - 1) % StackCacheSize;
v = m->stackcache[pos];
m->stackcachepos = pos;
m->stackcachecnt--;
m->stackinuse++;
malloced = false;
} else
v = runtime·mallocgc(n, 0, FlagNoProfiling|FlagNoGC|FlagNoZero|FlagNoInvokeGC);
top = (Stktop*)((byte*)v+n-sizeof(Stktop));
runtime·memclr((byte*)top, sizeof(*top));
top->malloced = malloced;
return v;
}
