mxqd starts user processes with SIGPIPE ignored #71
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donald
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Mar 20, 2018
The mysql client library sets SIGPIPE to SIG_IGN which gets inherited by
the user processes:
root@sigchld:~# cat /proc/27900/status |grep Sig
SigQ: 0/30656
SigPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000001000
SigCgt: 0000000000000000
This makes a difference for things like
CMD | head -1
because CMD is not killed by SIGPIPE when `head` is finished. It will get
an error "broken pipe" on the next write and may or may not emit this to
stderr.
This bug war partially caused by #63, where we changed our own signal
handling to synchronous mode. While in the previous mode, we unknowingly
fixed the change done by the mysql library, we then just set and
reset the blocking mask, which doesn't restore an ignored signal.
Restore SIGCHLD to SIG_DFL when we initialize the child process for the
user.
With this patch applied, no more signals are blocked for the user
process.
buczek@theinternet:~/git/mxq (restore-sigpipe)$ cat /proc/17081/status |grep Sig
SigQ: 1/127301
SigPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
Fixes #71
Merged
pmenzel
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that referenced
this issue
Mar 20, 2018
The mysql client library sets SIGPIPE to SIG_IGN which gets inherited by
the user processes:
root@sigchld:~# cat /proc/27900/status |grep Sig
SigQ: 0/30656
SigPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000001000
SigCgt: 0000000000000000
This makes a difference for things like
CMD | head -1
because CMD is not killed by SIGPIPE when `head` is finished. It will get
an error "broken pipe" on the next write and may or may not emit this to
stderr.
This bug was partially caused by #63 (commit ff2f49f (mxqd: Use
synchronous signals)), where we changed our own signal handling to
synchronous mode. While in the previous mode, we unknowingly fixed the
change done by the mysql library, we then just set and reset the blocking
mask, which doesn't restore an ignored signal.
Restore SIGCHLD to SIG_DFL when we initialize the child process for the
user.
With this patch applied, no more signals are blocked for the user
process.
buczek@theinternet:~/git/mxq (restore-sigpipe)$ cat /proc/17081/status |grep Sig
SigQ: 1/127301
SigPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
Fixes: #71
donald
added a commit
to mariux64/bee-files
that referenced
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Mar 21, 2018
Includes pull request mariux64/mxq#72 for issue mariux64/mxq#71 "mxqd starts user processes with SIGPIPE ignored"
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This makes a difference for things like
because CMD is not killed by sigpipe when head is finished, it will get an error "broken pipe" on the next write and may or may not emit this to stderr.
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