When a function created by cgo or SWIG returns an interface type and at
runtime returns a value that requires allocation when converting to
interface, it will call the memory allocation routine while appearing to
be in a system call. In particular there will be no memory cache
allocated. This patch permits this case to work. Bootstrapped and ran
Go testsuite on x86_64-unknown-linux-gnu. Committed to mainline and 4.8
branch.
Ian
diff -r bc94be12533f libgo/runtime/malloc.goc
--- a/libgo/runtime/malloc.goc Wed Jul 24 10:36:05 2013 -0700
+++ b/libgo/runtime/malloc.goc Wed Jul 24 15:22:39 2013 -0700
@@ -41,11 +41,24 @@
uintptr npages;
MSpan *s;
void *v;
+ bool incallback;
m = runtime_m();
g = runtime_g();
- if(g->status == Gsyscall)
- dogc = 0;
+
+ incallback = false;
+ if(m->mcache == nil && g->ncgo > 0) {
+ // For gccgo this case can occur when a cgo or SWIG function
+ // has an interface return type and the function
+ // returns a non-pointer, so memory allocation occurs
+ // after syscall.Cgocall but before syscall.CgocallDone.
+ // We treat it as a callback.
+ runtime_exitsyscall();
+ m = runtime_m();
+ incallback = true;
+ dogc = false;
+ }
+
if(runtime_gcwaiting && g != m->g0 && m->locks == 0 && dogc) {
runtime_gosched();
m = runtime_m();
@@ -129,6 +142,10 @@
runtime_racemalloc(v, size, m->racepc);
m->racepc = nil;
}
+
+ if(incallback)
+ runtime_entersyscall();
+
return v;
}
