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The various forkAndExecInChild implementations have comments
explaining that they pre-declare variables to force allocations
to occur before forking, but then later use ":=" declarations
for additional variables.
To make it clearer that those ":=" declarations do not allocate,
we move their declarations up to the predeclared blocks.
For #57208.
Change-Id: Ie8cb577fa7180b51b64d6dc398169053fdf8ea97
Reviewed-on: https://go-review.googlesource.com/c/go/+/456516
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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After dup'ing file descriptors in syscall.ProcAttr.Files to pass
to the exec'ed process, the logic for closing the old descriptors
was incorrect and could close the new descriptor instead.
Fixes #57180
Change-Id: I7725f21a465ffba57050fe4e36f3d36ba181cfb2
Reviewed-on: https://go-review.googlesource.com/c/go/+/457115
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
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Change-Id: Iae290216687fd1ce8be720600157fb78cc2446d0
GitHub-Last-Rev: 4fba64ecb14a704d39f6ecc33989522bcac6656f
GitHub-Pull-Request: golang/go#55959
Reviewed-on: https://go-review.googlesource.com/c/go/+/436881
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
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A future change to gofmt will rewrite
// Doc comment.
//go:foo
to
// Doc comment.
//
//go:foo
Apply that change preemptively to all comments (not necessarily just doc comments).
For #51082.
Change-Id: Iffe0285418d1e79d34526af3520b415a12203ca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/384260
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
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This replaces five implementations scattered across low level packages.
(And I plan to use it in a sixth soon.)
Three of the five were byte-for-byte identical.
Change-Id: I3bbbeeac63723a487986c912b604e10ad1e042f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/301549
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
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Change Plan 9 fork/exec to use the O_CLOEXEC file
descriptor, instead of relying on spooky at a
distance.
Historically, Plan 9 has set the O_CLOEXEC flag on
the underlying channels in the kernel, rather
than the file descriptors -- if two fds pointed
at a single channel, as with dup, changing the
flags on one of them would be observable on the
other.
The per-Chan semantics are ok, if unexpected,
when a chan is only handled within a single
process, but this isn't always the case.
Forked processes share Chans, but even more of
a problem is the interaction between /srv and
OCEXEC, which can lead to unexectedly closed
file descriptors in completely unrelated
proceses. For example:
func exists() bool {
// If some other thread execs here,
// we don't want to leak the fd, so
// open it O_CLOEXEC
fd := Open("/srv/foo", O_CLOEXEC)
if fd != -1 {
Close(fd)
return true
}
return false
}
would close the connection to any file descriptor
(maybe even for the root fs) in ALL other processes
that have it open if an exec were to happen(!),
which is quite undesriable.
As a result, 9front will be changing this behavior
for the next release.
Go is the only code observed so far that relies on
this behavior on purpose, and It's easy to make the
code work with both semantics: simply using the file
descriptor that was opened with O_CEXEC instead of
throwing it away.
So we do that here.
Fixes #43524
Change-Id: I4887f5c934a5e63e5e6c1bb59878a325abc928d3
GitHub-Last-Rev: 96bb21bd1e8f64dc7e082a56928748a7d54c9272
GitHub-Pull-Request: golang/go#43533
Reviewed-on: https://go-review.googlesource.com/c/go/+/281833
Reviewed-by: David du Colombier <0intro@gmail.com>
Reviewed-by: Richard Miller <millerresearch@gmail.com>
Reviewed-by: Jacob Moody <j4kem00dy@gmail.com>
Run-TryBot: David du Colombier <0intro@gmail.com>
Trust: Ian Lance Taylor <iant@golang.org>
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Change-Id: Iacedb792c73591b7fd75e836aab8e0e117c8e738
Reviewed-on: https://go-review.googlesource.com/27494
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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This is the follow-on to CL 22610: now that it's the child instead of
the parent which lists unwanted fds to close in syscall.StartProcess,
plan9 no longer needs the ForkLock to protect the list from changing.
The readdupdevice function is also now unused and can be removed.
Change-Id: I904c8bbf5dbaa7022b0f1a1de0862cd3064ca8c7
Reviewed-on: https://go-review.googlesource.com/22842
Reviewed-by: David du Colombier <0intro@gmail.com>
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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Reviving earlier work by @ality in https://golang.org/cl/57890043
to make the closing of extra file descriptors in syscall.StartProcess
less race-prone. Instead of making a list of open fds in the parent
before forking, the child can read through the list of open fds and
close the ones not explicitly requested. Also eliminate the
complication of keeping open any extra fds which were inherited by
the parent when it started.
This CL will be followed by one to eliminate the ForkLock in plan9,
which is now redundant.
Fixes #5605
Change-Id: I6b4b942001baa54248b656c52dced3b62021c486
Reviewed-on: https://go-review.googlesource.com/22610
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
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In syscall.forkAndExecInChild, blocks of code labelled Pass 1
and Pass 2 permute the file descriptors (if necessary) which are
passed to the child process. If Pass 1 begins with fds = {0,2,1},
nextfd = 4 and pipe = 4, then the statement labelled "don't stomp
on pipe" is too late -- the pipe (which will be needed to pass
exec status back to the parent) will have been closed by the
preceding DUP call.
Moving the "don't stomp" test earlier ensures that the pipe is
protected.
Fixes #14979
Change-Id: I890c311527f6aa255be48b3277c1e84e2049ee22
Reviewed-on: https://go-review.googlesource.com/21184
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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Between the enumeration of fdsToClose in the parent and the
closing of fds in the child, it's possible for a file to be
closed in another thread. If that file descriptor is reused
when opening the child-parent status pipe, it will be closed
prematurely in the child and the forkExec gets out of sync.
This has been observed to cause failures in builder tests
when the link step of a build is started before the compile
step has run, with "file does not exist" messages as the
visible symptom.
The simple workaround is to check against closing the pipe.
A more comprehensive solution would be to rewrite the fd
closing code to avoid races, along the lines of the long
ago proposed https://golang.org/cl/57890043 - but meanwhile
this correction will prevent some builder failures.
Change-Id: I4ef5eaea70c21d00f4df0e0847a1c5b2966de7da
Reviewed-on: https://go-review.googlesource.com/20800
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
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The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.
This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:
$ perl -i -npe 's,^(\s*// .+[a-z]\.) +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.) +([A-Z])')
$ go test go/doc -update
Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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On multiprocessor machines, a file descriptor could be
closed twice in forkAndExecInChild. Consequently, the close
syscall returns the "fd out of range or not open" error
and forkAndExecInChild fails.
This changes forkAndExecInChild to ignore the error
returned by close(fd), as on other operating systems.
Fixes #12851.
Change-Id: I96a8463ce6599bfd1362353283e0329a00f738da
Reviewed-on: https://go-review.googlesource.com/17188
Reviewed-by: Rob Pike <r@golang.org>
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Use a go:norace comment rather than having the compiler know the special
name syscall.forkAndExecInChild.
Change-Id: I69bc6aa6fc40feb2148d23f269ff32453696fb28
Reviewed-on: https://go-review.googlesource.com/16097
Reviewed-by: Minux Ma <minux@golang.org>
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While we're at it, move some misplaced comment blocks around.
Change-Id: I1847d7f1ca1dbb8e5de737203c4ed6c66e112508
Reviewed-on: https://go-review.googlesource.com/10188
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
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On Plan 9, the pwd is apparently per-thread not per process. That
means different goroutines saw different current directories, even
changing within a goroutine as they were scheduled.
Instead, track the the process-wide pwd protected by a mutex in the
syscall package and set the current goroutine thread's pwd to the
correct once at critical points.
Fixes #9428
Change-Id: I928e90886355be4a95c2be834f5883e2b50fc0cf
Reviewed-on: https://go-review.googlesource.com/6350
Reviewed-by: David du Colombier <0intro@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.
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