Skip to content

syscall: stuck at syscall.Write #44083

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
jarifibrahim opened this issue Feb 3, 2021 · 8 comments
Closed

syscall: stuck at syscall.Write #44083

jarifibrahim opened this issue Feb 3, 2021 · 8 comments
Labels
FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.

Comments

@jarifibrahim
Copy link

What version of Go are you using (go version)?

$ go version
go version go1.15.6 linux/amd64

Does this issue reproduce with the latest release?

Probably not.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/dg/.cache/go-build"
GOENV="/home/dg/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/dg/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/dg/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/snap/go/6745"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/snap/go/6745/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build185691020=/tmp/go-build -gno-record-gcc-switches"

What did you do?

This issue might not be reproducible.

I was running dgraph bulk loader https://github.com/dgraph-io/dgraph $ dgraph bulk .... The process has been stuck for more than 30+ hours now. I'm looking at the goroutine dump and I see the following

goroutine 25531 [syscall, 3153 minutes]:
syscall.Syscall(0x1, 0x2, 0xc005c4bc00, 0x5c, 0x8, 0x7fffffffffffffff, 0x6017abfd)
	/snap/go/6745/src/syscall/asm_linux_amd64.s:18 +0x5
syscall.write(0x2, 0xc005c4bc00, 0x5c, 0x80, 0x4d58, 0x3, 0xc000044c29)
	/snap/go/6745/src/syscall/zsyscall_linux_amd64.go:914 +0x5a
syscall.Write(...)
	/snap/go/6745/src/syscall/syscall_unix.go:212
internal/poll.(*FD).Write.func1(0x7ffff80000000000, 0x4, 0xc0000a612c)
	/snap/go/6745/src/internal/poll/fd_unix.go:267 +0x77
internal/poll.ignoringEINTR(0xc00008bc10, 0x77, 0xed7a9a201, 0x0)
	/snap/go/6745/src/internal/poll/fd_unix.go:567 +0x27
internal/poll.(*FD).Write(0xc0000a6120, 0xc005c4bc00, 0x5c, 0x80, 0x0, 0x0, 0x0)
	/snap/go/6745/src/internal/poll/fd_unix.go:267 +0x19c
os.(*File).write(...)
	/snap/go/6745/src/os/file_posix.go:48
os.(*File).Write(0xc000010020, 0xc005c4bc00, 0x5c, 0x80, 0x29a60a0, 0x0, 0x0)
	/snap/go/6745/src/os/file.go:173 +0x77
log.(*Logger).Output(0xc000241450, 0x2, 0xc1ef10a140, 0x41, 0x0, 0x0)
	/snap/go/6745/src/log/log.go:181 +0x284
log.(*Logger).Printf(0xc000241450, 0xc030b9c7c0, 0x3e, 0xc065dd6740, 0x4, 0x4)
	/snap/go/6745/src/log/log.go:188 +0x7e
github.com/dgraph-io/badger/v3.(*defaultLog).Infof(0xc0004641f0, 0x1dbb913, 0x38, 0xc065dd6740, 0x4, 0x4)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/logger.go:97 +0xc5
github.com/dgraph-io/badger/v3.(*Options).Infof(...)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/logger.go:46
github.com/dgraph-io/badger/v3.(*sortedWriter).createTable(0xc000ace000, 0xc00004c680, 0x0, 0x0)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:454 +0x542
github.com/dgraph-io/badger/v3.(*sortedWriter).send.func1(0xc000ace000, 0xc00004c680)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:384 +0x35
created by github.com/dgraph-io/badger/v3.(*sortedWriter).send
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:383 +0x86

The file that we're writing to is a usual file and I can read/write to that file.
It looks like the syscall has been stuck for 3153 minutes. Since this syscall is stuck, dgraph bulk is also stuck and I see a bunch of goroutines trying to acquire the lock

goroutine 25172 [semacquire, 3153 minutes]:
sync.runtime_SemacquireMutex(0xc000241454, 0x6017ac00, 0x1)
	/snap/go/6745/src/runtime/sema.go:71 +0x47
sync.(*Mutex).lockSlow(0xc000241450)
	/snap/go/6745/src/sync/mutex.go:138 +0x105
sync.(*Mutex).Lock(...)
	/snap/go/6745/src/sync/mutex.go:81
log.(*Logger).Output(0xc000241450, 0x2, 0xc1ef10a320, 0x41, 0x0, 0x0)
	/snap/go/6745/src/log/log.go:162 +0x40e
log.(*Logger).Printf(0xc000241450, 0xc020aed000, 0x3e, 0xc0039e3540, 0x4, 0x4)
	/snap/go/6745/src/log/log.go:188 +0x7e
github.com/dgraph-io/badger/v3.(*defaultLog).Infof(0xc0004641f0, 0x1dbb913, 0x38, 0xc0039e3540, 0x4, 0x4)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/logger.go:97 +0xc5
github.com/dgraph-io/badger/v3.(*Options).Infof(...)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/logger.go:46
github.com/dgraph-io/badger/v3.(*sortedWriter).createTable(0xc000ace0b0, 0xc0003ba580, 0x0, 0x0)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:454 +0x542
github.com/dgraph-io/badger/v3.(*sortedWriter).send.func1(0xc000ace0b0, 0xc0003ba580)
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:384 +0x35
created by github.com/dgraph-io/badger/v3.(*sortedWriter).send
	/home/dg/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/stream_writer.go:383 +0x86

I've also attached the complete goroutine dump
goroutine.txt

What did you expect to see?

I expected the logger to not get stuck 🤷‍♂️

What did you see instead?

The log/log.go was stuck because a syscall wasn't making progress.
@seankhliao seankhliao changed the title log/log.go: Logger stuck at syscall.Write syscall: stuck at syscall.Write Feb 3, 2021
@seankhliao seankhliao added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Feb 3, 2021
@networkimprov
Copy link

cc @ianlancetaylor

@ianlancetaylor
Copy link
Member

Thanks for the bug report, but it's hard to see how this is a problem in Go. The stack trace shows that Go is calling the system call write. That system call is not returning. I don't know why that is happening, but it seems like a kernel problem, not a problem in Go.

It would certainly be worth investigating if this is reproducible.

@ianlancetaylor ianlancetaylor added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Feb 5, 2021
@networkimprov
Copy link

Is the file in question on a network filesystem, e.g. NFS?

Also the poller retries EINTR from syscalls, which can result in hangs.

@ianlancetaylor
Copy link
Member

I don't see any way that retrying on EINTR could introduce a hang on the write system call. The write has to hang for some other reason.

In any case that is not what happened here. The goroutine stack trace shows that the goroutine has been waiting for the write system call to return for 3153 minutes. If there was some sort of EINTR loop, that number would be lower.

@jarifibrahim
Copy link
Author

jarifibrahim commented Feb 5, 2021 •
edited
Loading

Is the file in question on a network filesystem, e.g. NFS?

@networkimprov No. This was a normal file on a local SSD.

@networkimprov
Copy link

Seems likely to be a transient hardware problem or kernel bug. A watchdog that can abort the app may be the only solution.

@mvdan
Copy link
Member

mvdan commented Jun 15, 2021

Closing old issues that still have the WaitingForInfo label where enough details to investigate weren't provided. Feel free to leave a comment with more details and we can reopen.

@mvdan mvdan closed this as completed Jun 15, 2021
@youguanxinqing
Copy link

@jarifibrahim hi jarifibrahim! I also have met the issue. Did you solve it?

@golang golang locked and limited conversation to collaborators Apr 29, 2023
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Assignees
No one assigned
Labels
FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
7 participants
@networkimprov @ianlancetaylor @mvdan @gopherbot @seankhliao @jarifibrahim @youguanxinqing