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runtime: efence support for growable stacks

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1. Fix the bug that shrinkstack returns memory to heap.
   This causes growslice to misbehave (it manually initialized
   blocks, and in efence mode shrinkstack's free leads to
   partially-initialized blocks coming out of growslice.
   Which in turn causes GC to crash while treating the garbage
   as Eface/Iface.
2. Enable efence for stack segments.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, khr
https://golang.org/cl/74080043
This commit is contained in:
Dmitriy Vyukov 2014-03-12 10:21:34 +04:00
parent 00e6fc1e9e
commit 1f4d2e79b0
1 changed files with 12 additions and 4 deletions
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16
src/pkg/runtime/stack.c
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@ -102,7 +102,7 @@ runtime·stackalloc(G *gp, uint32 n)
runtime·printf("stackalloc %d\n", n);
gp->stacksize += n;
if(StackFromSystem)
if(runtime·debug.efence || StackFromSystem)
return runtime·SysAlloc(ROUND(n, PageSize), &mstats.stacks_sys);
// Minimum-sized stacks are allocated with a fixed-size free-list allocator,
@ -143,8 +143,8 @@ runtime·stackfree(G *gp, void *v, Stktop *top)
if(StackDebug >= 1)
runtime·printf("stackfree %p %d\n", v, (int32)n);
gp->stacksize -= n;
if(StackFromSystem) {
if(StackFaultOnFree)
if(runtime·debug.efence || StackFromSystem) {
if(runtime·debug.efence || StackFaultOnFree)
runtime·SysFault(v, n);
else
runtime·SysFree(v, n, &mstats.stacks_sys);
@ -819,7 +819,15 @@ runtime·shrinkstack(G *gp)
gp->stack0 = (uintptr)oldstk + newsize;
gp->stacksize -= oldsize - newsize;
// Free bottom half of the stack. First, we trick malloc into thinking
// Free bottom half of the stack.
if(runtime·debug.efence || StackFromSystem) {
if(runtime·debug.efence || StackFaultOnFree)
runtime·SysFault(oldstk, newsize);
else
runtime·SysFree(oldstk, newsize, &mstats.stacks_sys);
return;
}
// First, we trick malloc into thinking
// we allocated the stack as two separate half-size allocs. Then the
// free() call does the rest of the work for us.
if(oldsize == PageSize) {