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syscall: linux/386 socketcall uintptr #7169

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bradfitz opened this issue Jan 22, 2014 · 3 comments
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syscall: linux/386 socketcall uintptr #7169

bradfitz opened this issue Jan 22, 2014 · 3 comments
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@bradfitz
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@bradfitz bradfitz commented Jan 22, 2014

This looks suspect for precise GC:

// On x86 Linux, all the socket calls go through an extra indirection,
// I think because the 5-register system call interface can't handle
// the 6-argument calls like sendto and recvfrom.  Instead the
// arguments to the underlying system call are the number below
// and a pointer to an array of uintptr.  We hide the pointer in the
// socketcall assembly to avoid allocation on every system call.

const (
    // see linux/net.h
    _SOCKET      = 1
    _BIND        = 2
    _CONNECT     = 3
    _LISTEN      = 4
    _ACCEPT      = 5
    _GETSOCKNAME = 6
    _GETPEERNAME = 7
    _SOCKETPAIR  = 8
    _SEND        = 9
    _RECV        = 10
    _SENDTO      = 11
    _RECVFROM    = 12
    _SHUTDOWN    = 13
    _SETSOCKOPT  = 14
    _GETSOCKOPT  = 15
    _SENDMSG     = 16
    _RECVMSG     = 17
    _ACCEPT4     = 18
    _RECVMMSG    = 19
    _SENDMMSG    = 20
)

func socketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err Errno)
func rawsocketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err Errno)
@bradfitz
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@bradfitz bradfitz commented Jan 22, 2014

Comment 1:

Related: http://build.golang.org/log/47cb3e4ed7ea45d74ada437a8dfbec552a7f59c7 crash and
email thread [golang-dev] dragonfly-386 broken by runtime: fix specials deadlock
@bradfitz
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@bradfitz bradfitz commented Jan 22, 2014

Comment 2:

This issue was updated by revision f00af3d.

R=rsc
CC=golang-codereviews
https://golang.org/cl/55410043
@bradfitz
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@bradfitz bradfitz commented Jan 22, 2014

Comment 3:

False alarm.  socketcall and rawsocketcall are NOSPLIT:
TEXT ·socketcall(SB),NOSPLIT,$0-40
TEXT ·rawsocketcall(SB),NOSPLIT,$0-40
So there should be no preemptions to do a GC.  I see no callers of socketcall or
rawsocketcall that have a pointer disappear into a uintptr over a pre-emptable function
call.
I think this is now fully fixed by revision 87208c254908.

Owner changed to @bradfitz.

Status changed to Fixed.

@bradfitz bradfitz added fixed labels Jan 22, 2014
@bradfitz bradfitz self-assigned this Jan 22, 2014
@rsc rsc added this to the Go1.3 milestone Apr 14, 2015
@rsc rsc removed the release-go1.3 label Apr 14, 2015
@golang golang locked and limited conversation to collaborators Jun 25, 2016
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