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runtime: fatal error: bad pointer in write barrier on linux-s390x-ibm #15270

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mikioh opened this issue Apr 13, 2016 · 4 comments
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runtime: fatal error: bad pointer in write barrier on linux-s390x-ibm #15270

mikioh opened this issue Apr 13, 2016 · 4 comments
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Go1.7

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@mikioh
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mikioh commented Apr 13, 2016

See http://build.golang.org/log/0c4bb957f324e4371f4364878cc79d42c57187b5

ok      regexp  0.074s
ok      regexp/syntax   0.388s
runtime: writebarrierptr *0x3503d0 = 0x400
fatal error: bad pointer in write barrier

runtime stack:
runtime.throw(0x26eb38, 0x1c)
    /data/golang/workdir/go/src/runtime/panic.go:566 +0x96 fp=0x3ff8dc7eee0 sp=0x3ff8dc7eec8
runtime.writebarrierptr.func1()
    /data/golang/workdir/go/src/runtime/mbarrier.go:140 +0xc0 fp=0x3ff8dc7ef08 sp=0x3ff8dc7eee0
runtime.systemstack(0xc82001a000)
    /data/golang/workdir/go/src/runtime/asm_s390x.s:249 +0x9a fp=0x3ff8dc7ef10 sp=0x3ff8dc7ef08
runtime.mstart()
    /data/golang/workdir/go/src/runtime/proc.go:1077 fp=0x3ff8dc7ef10 sp=0x3ff8dc7ef10
(snip)

/CC @aclements
@mikioh mikioh added this to the Go1.7 milestone Apr 13, 2016
@bradfitz
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/cc @mundaym

@aclements
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It looks like atomic.Storep1 on s390 generates a write barrier. On other platforms it does not (that's what runtime.atomicstorep is for, though this appears to be completely undocumented).

Going a little further down, here's where the "bad pointer write" actually happened:

goroutine 102586 [running]:
runtime.systemstack_switch()
    /data/golang/workdir/go/src/runtime/asm_s390x.s:203 +0x10 fp=0xc820409be8 sp=0xc820409be0
runtime.writebarrierptr(0x3503d0, 0x400)
    /data/golang/workdir/go/src/runtime/mbarrier.go:141 +0xd2 fp=0xc820409c18 sp=0xc820409be8
runtime/internal/atomic.Storep1(0x3503d0, 0x400)
    /data/golang/workdir/go/src/runtime/internal/atomic/atomic_s390x.go:43 +0x56 fp=0xc820409c30 sp=0xc820409c18
runtime.mapzero(0x206f80)
    /data/golang/workdir/go/src/runtime/hashmap.go:1079 +0x13a fp=0xc820409c60 sp=0xc820409c30
...

This is actually a scalar write (the zerosize global), but we're doing it using an atomic pointer write (yuck!).

I'll send a CL.

@gopherbot
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CL https://golang.org/cl/21993 mentions this issue.

@gopherbot
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CL https://golang.org/cl/21994 mentions this issue.

gopherbot pushed a commit that referenced this issue Apr 13, 2016
@aclements
runtime/internal/atomic: rename Storep1 to StorepNoWB
4721ea6 
Make it clear that the point of this function stores a pointer
*without* a write barrier.

sed -i -e 's/Storep1/StorepNoWB/' $(git grep -l Storep1)

Updates #15270.

Change-Id: Ifad7e17815e51a738070655fe3b178afdadaecf6
Reviewed-on: https://go-review.googlesource.com/21994
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
@golang golang locked and limited conversation to collaborators Apr 13, 2017
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