Why doesn't the Linux kernel send SIGCONT first and then SIGHUP to a newly orphaned process group containing a stopped process?
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APUE says
Since the process group is orphaned when the parent terminates, and the
process group contains a stopped process, POSIX.1 requires that every process in
the newly orphaned process group be sent the hang-up signal (SIGHUP)
followed by the continue signal (SIGCONT).
The kernel sends SIGCONT after SIGHUP, but the process is waken up by SIGCONT before acting on SIGHUP. So why doesn't the Linux kernel send SIGCONT before SIGHUP?
Thanks.
Related to but not answered by Does the default action of SIGCONT resume the execution of a stopped process before or after first handling any pending unblocked signals?
I did not answer my question.
linux signals sighup
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
add a comment |
APUE says
Since the process group is orphaned when the parent terminates, and the
process group contains a stopped process, POSIX.1 requires that every process in
the newly orphaned process group be sent the hang-up signal (SIGHUP)
followed by the continue signal (SIGCONT).
The kernel sends SIGCONT after SIGHUP, but the process is waken up by SIGCONT before acting on SIGHUP. So why doesn't the Linux kernel send SIGCONT before SIGHUP?
Thanks.
Related to but not answered by Does the default action of SIGCONT resume the execution of a stopped process before or after first handling any pending unblocked signals?
I did not answer my question.
linux signals sighup
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
3
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58
add a comment |
APUE says
Since the process group is orphaned when the parent terminates, and the
process group contains a stopped process, POSIX.1 requires that every process in
the newly orphaned process group be sent the hang-up signal (SIGHUP)
followed by the continue signal (SIGCONT).
The kernel sends SIGCONT after SIGHUP, but the process is waken up by SIGCONT before acting on SIGHUP. So why doesn't the Linux kernel send SIGCONT before SIGHUP?
Thanks.
Related to but not answered by Does the default action of SIGCONT resume the execution of a stopped process before or after first handling any pending unblocked signals?
I did not answer my question.
linux signals sighup
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
APUE says
Since the process group is orphaned when the parent terminates, and the
process group contains a stopped process, POSIX.1 requires that every process in
the newly orphaned process group be sent the hang-up signal (SIGHUP)
followed by the continue signal (SIGCONT).
The kernel sends SIGCONT after SIGHUP, but the process is waken up by SIGCONT before acting on SIGHUP. So why doesn't the Linux kernel send SIGCONT before SIGHUP?
Thanks.
Related to but not answered by Does the default action of SIGCONT resume the execution of a stopped process before or after first handling any pending unblocked signals?
I did not answer my question.
linux signals sighup
linux signals sighup
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
edited Dec 26 '18 at 20:13
Tim
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
asked Dec 26 '18 at 13:46
TimTim
26.3k74246455
26.3k74246455
3
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58
add a comment |
3
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58
3
3
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58
add a comment |
1 Answer
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oldest
votes
Not only do you answer your question, the link you added at the end also answers your question.
When a process is stopped, all signal processing is stopped, except for SIGCONT and SIGKILL - which are, in practice handled by the operating system.
This means that SIGHUP can only the handled after the process is resumed, which happens when SIGCONT is recieved and handled, so, even if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order.
Now, in practice, the kernel sending SIGHUP before will result in less stuff being done by a process between handling SIGCONT and handling SIGHUP, as the second is already queued to be handled.
answered Dec 26 '18 at 19:02
theMagetheMage
462
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
add a comment |
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1 Answer
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1 Answer
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oldest
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votes
Not only do you answer your question, the link you added at the end also answers your question.
When a process is stopped, all signal processing is stopped, except for SIGCONT and SIGKILL - which are, in practice handled by the operating system.
This means that SIGHUP can only the handled after the process is resumed, which happens when SIGCONT is recieved and handled, so, even if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order.
Now, in practice, the kernel sending SIGHUP before will result in less stuff being done by a process between handling SIGCONT and handling SIGHUP, as the second is already queued to be handled.
answered Dec 26 '18 at 19:02
theMagetheMage
462
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
add a comment |
Not only do you answer your question, the link you added at the end also answers your question.
When a process is stopped, all signal processing is stopped, except for SIGCONT and SIGKILL - which are, in practice handled by the operating system.
This means that SIGHUP can only the handled after the process is resumed, which happens when SIGCONT is recieved and handled, so, even if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order.
Now, in practice, the kernel sending SIGHUP before will result in less stuff being done by a process between handling SIGCONT and handling SIGHUP, as the second is already queued to be handled.
answered Dec 26 '18 at 19:02
theMagetheMage
462
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
add a comment |
Not only do you answer your question, the link you added at the end also answers your question.
When a process is stopped, all signal processing is stopped, except for SIGCONT and SIGKILL - which are, in practice handled by the operating system.
This means that SIGHUP can only the handled after the process is resumed, which happens when SIGCONT is recieved and handled, so, even if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order.
Now, in practice, the kernel sending SIGHUP before will result in less stuff being done by a process between handling SIGCONT and handling SIGHUP, as the second is already queued to be handled.
answered Dec 26 '18 at 19:02
theMagetheMage
462
Not only do you answer your question, the link you added at the end also answers your question.
When a process is stopped, all signal processing is stopped, except for SIGCONT and SIGKILL - which are, in practice handled by the operating system.
This means that SIGHUP can only the handled after the process is resumed, which happens when SIGCONT is recieved and handled, so, even if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order.
Now, in practice, the kernel sending SIGHUP before will result in less stuff being done by a process between handling SIGCONT and handling SIGHUP, as the second is already queued to be handled.
answered Dec 26 '18 at 19:02
theMagetheMage
462
answered Dec 26 '18 at 19:02
theMagetheMage
462
answered Dec 26 '18 at 19:02
theMagetheMage
462
answered Dec 26 '18 at 19:02
theMagetheMage
462
462
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
add a comment |
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
This is the part that I am not sure: "if you send a SIGHUP followed by a SIGCONT, they are going to be handled in the opposite order."
– Tim
Dec 26 '18 at 20:13
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
Hi @Tim. If the process is stopped, they have to be, because until the process handles SIGCONT, it doesn't handle any other signal, except SIGCONT and SIGKILL.
– theMage
Dec 27 '18 at 9:09
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
So isn't it the same reacting order, regardless of sending order?
– Tim
Dec 27 '18 at 12:29
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
It is. However, you can't warranty that the process sending the signals will not be paused between serving the two signals, which would, potentially, resulting in the second process doing other stuff between handling the two signals.
– theMage
Dec 27 '18 at 16:19
add a comment |
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3
You just answered your own question; to ensure SIGHUP is pending and so handled when the process is resumed.
– Stephen Harris
Dec 26 '18 at 13:58