Issue 4216045: code review 4216045: runtime: always run stackalloc on scheduler stack

Issue 4216045: code review 4216045: runtime: always run stackalloc on scheduler stack (Closed)

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Created:
14 years, 3 months ago by rsc

Modified:
14 years, 3 months ago

Reviewers:

CC:
r, r2, golang-dev

Visibility:
Public.

Description

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) ...

	Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+45 lines, -9 lines)			Patch
M	src/pkg/runtime/malloc.goc	View	1	1 chunk	+6 lines, -0 lines	0 comments	Download
M	src/pkg/runtime/mgc0.c	View	1	1 chunk	+1 line, -0 lines	0 comments	Download
M	src/pkg/runtime/proc.c	View	1 2	4 chunks	+37 lines, -9 lines	0 comments	Download
M	src/pkg/runtime/runtime.h	View	1	1 chunk	+1 line, -0 lines	0 comments	Download

Messages

Total messages: 3

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rsc

Hello r (cc: golang-dev@googlegroups.com), I'd like you to review this change to https://go.googlecode.com/hg

14 years, 3 months ago (2011-02-23 20:45:09 UTC) #1

rsc

14 years, 3 months ago (2011-02-23 20:51:22 UTC) #3

*** Submitted as 35425edd2f49 ***

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
http://codereview.appspot.com/4216045

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