From b5dfac45ba29f12cbc86925ab7c7cd018f87f4fe Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 23 Feb 2011 15:51:20 -0500 Subject: runtime: always run stackalloc on scheduler stack Avoids deadlocks like the one below, in which a stack split happened in order to call lock(&stacks), but then the stack unsplit cannot run because stacks is now locked. The only code calling stackalloc that wasn't on a scheduler stack already was malg, which creates a new goroutine. runtime.futex+0x23 /home/rsc/g/go/src/pkg/runtime/linux/amd64/sys.s:139 runtime.futex() futexsleep+0x50 /home/rsc/g/go/src/pkg/runtime/linux/thread.c:51 futexsleep(0x5b0188, 0x300000003, 0x100020000, 0x4159e2) futexlock+0x85 /home/rsc/g/go/src/pkg/runtime/linux/thread.c:119 futexlock(0x5b0188, 0x5b0188) runtime.lock+0x56 /home/rsc/g/go/src/pkg/runtime/linux/thread.c:158 runtime.lock(0x5b0188, 0x7f0d27b4a000) runtime.stackfree+0x4d /home/rsc/g/go/src/pkg/runtime/malloc.goc:336 runtime.stackfree(0x7f0d27b4a000, 0x1000, 0x8, 0x7fff37e1e218) runtime.oldstack+0xa6 /home/rsc/g/go/src/pkg/runtime/proc.c:705 runtime.oldstack() runtime.lessstack+0x22 /home/rsc/g/go/src/pkg/runtime/amd64/asm.s:224 runtime.lessstack() ----- lessstack called from goroutine 2 ----- runtime.lock+0x56 /home/rsc/g/go/src/pkg/runtime/linux/thread.c:158 runtime.lock(0x5b0188, 0x40a5e2) runtime.stackalloc+0x55 /home/rsc/g/go/src/pkg/runtime/malloc.c:316 runtime.stackalloc(0x1000, 0x4055b0) runtime.malg+0x3d /home/rsc/g/go/src/pkg/runtime/proc.c:803 runtime.malg(0x1000, 0x40add9) runtime.newproc1+0x12b /home/rsc/g/go/src/pkg/runtime/proc.c:854 runtime.newproc1(0xf840027440, 0x7f0d27b49230, 0x0, 0x49f238, 0x40, ...) runtime.newproc+0x2f /home/rsc/g/go/src/pkg/runtime/proc.c:831 runtime.newproc(0x0, 0xf840027440, 0xf800000010, 0x44b059) ... R=r, r2 CC=golang-dev https://golang.org/cl/4216045 --- src/pkg/runtime/malloc.goc | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'src/pkg/runtime/malloc.goc') diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc index abbf63b931..41060682eb 100644 --- a/src/pkg/runtime/malloc.goc +++ b/src/pkg/runtime/malloc.goc @@ -394,6 +394,12 @@ runtime·stackalloc(uint32 n) { 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"); + if(m->mallocing || m->gcing || n == FixedStack) { runtime·lock(&stacks); if(stacks.size == 0) -- cgit v1.3