[LTP] [PATCH] Synchronization between two processes

[LTP] [PATCH] Synchronization between two processes

[Gui Xiaohua]

The child-process wait SIGUSR1 which would be sended by parent-process,
if the child-process execute sigtimedwait() after parent-process send 
the signal, it would never receive the SIGUSR1 from parent-process.
I cann't make sure the SIGUSR1 be sended after child-process execute 
sigtimedwait() with 100 percent, and i try my best.

Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
--- testcases/kernel/containers/pidns/pidns12-old.c	2009-05-14 17:00:20.000000000 +0800
+++ testcases/kernel/containers/pidns/pidns12.c	2009-05-15 15:15:22.000000000 +0800
@@ -109,7 +109,7 @@ int child_fn(void *arg)
 	}
 
 	/* Set timeout for sigtimedwait */
-	timeout.tv_sec = 3;
+	timeout.tv_sec = 10;
 	timeout.tv_nsec = 0;
 
 	/* Set mask to wait for SIGUSR1 signal */
@@ -182,6 +182,9 @@ int main(int argc, char *argv[])
 		cleanup();
 	}
 
+	/*Try best to make sure the SIGUSR1 be sended after child-process execute sigtimedwait*/
+	sleep(5);
+
 	/* Send SIGUSR1 to container init */
 	if (kill(cpid, SIGUSR1) == -1) {
 		tst_resm(TBROK, "parent: kill() failed(%s).", strerror(errno));


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Re: [LTP] [PATCH] Synchronization between two processes

[Subrata Modak]

On Fri, 2009-05-15 at 15:04 +0800, Gui Xiaohua wrote:
> The child-process wait SIGUSR1 which would be sended by parent-process,
> if the child-process execute sigtimedwait() after parent-process send 
> the signal, it would never receive the SIGUSR1 from parent-process.
> I cann't make sure the SIGUSR1 be sended after child-process execute 
> sigtimedwait() with 100 percent, and i try my best.
> 
> Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>

Over to Serge.

Regards--
Subrata

> --- testcases/kernel/containers/pidns/pidns12-old.c	2009-05-14 17:00:20.000000000 +0800
> +++ testcases/kernel/containers/pidns/pidns12.c	2009-05-15 15:15:22.000000000 +0800
> @@ -109,7 +109,7 @@ int child_fn(void *arg)
>  	}
> 
>  	/* Set timeout for sigtimedwait */
> -	timeout.tv_sec = 3;
> +	timeout.tv_sec = 10;
>  	timeout.tv_nsec = 0;
> 
>  	/* Set mask to wait for SIGUSR1 signal */
> @@ -182,6 +182,9 @@ int main(int argc, char *argv[])
>  		cleanup();
>  	}
> 
> +	/*Try best to make sure the SIGUSR1 be sended after child-process execute sigtimedwait*/
> +	sleep(5);
> +
>  	/* Send SIGUSR1 to container init */
>  	if (kill(cpid, SIGUSR1) == -1) {
>  		tst_resm(TBROK, "parent: kill() failed(%s).", strerror(errno));
> 
> 
> ------------------------------------------------------------------------------
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> unlimited royalty-free distribution of the report engine 
> for externally facing server and web deployment. 
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Re: [LTP] [PATCH] Synchronization between two processes

[Serge E. Hallyn]

Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
> The child-process wait SIGUSR1 which would be sended by parent-process,
> if the child-process execute sigtimedwait() after parent-process send 
> the signal, it would never receive the SIGUSR1 from parent-process.
> I cann't make sure the SIGUSR1 be sended after child-process execute 
> sigtimedwait() with 100 percent, and i try my best.

Well, in theory I suppose this could happen, but you'd have to have
a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
between the pipe read and signal send, while the child goes straight
from pipe write to sigtimedwait.

Have you seen this signal be missed?  If not, then I'd rather assume
things are reasonable.  If you have seen this happen, then why not
instead set up a SIGUSR1 handler in the child before doing the pipe
write, then just sleep for 3 seconds instead of doing sigtimedwait?

> Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
> --- testcases/kernel/containers/pidns/pidns12-old.c	2009-05-14 17:00:20.000000000 +0800
> +++ testcases/kernel/containers/pidns/pidns12.c	2009-05-15 15:15:22.000000000 +0800
> @@ -109,7 +109,7 @@ int child_fn(void *arg)
>  	}
> 
>  	/* Set timeout for sigtimedwait */
> -	timeout.tv_sec = 3;
> +	timeout.tv_sec = 10;
>  	timeout.tv_nsec = 0;
> 
>  	/* Set mask to wait for SIGUSR1 signal */
> @@ -182,6 +182,9 @@ int main(int argc, char *argv[])
>  		cleanup();
>  	}
> 
> +	/*Try best to make sure the SIGUSR1 be sended after child-process execute sigtimedwait*/
> +	sleep(5);
> +
>  	/* Send SIGUSR1 to container init */
>  	if (kill(cpid, SIGUSR1) == -1) {
>  		tst_resm(TBROK, "parent: kill() failed(%s).", strerror(errno));
> 
> 
> ------------------------------------------------------------------------------
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> Check out the new simplified licensing option that enables 
> unlimited royalty-free distribution of the report engine 
> for externally facing server and web deployment. 
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Re: [LTP] [PATCH] Synchronization between two processes

[Subrata Modak]

On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote: 
> Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
> > The child-process wait SIGUSR1 which would be sended by parent-process,
> > if the child-process execute sigtimedwait() after parent-process send 
> > the signal, it would never receive the SIGUSR1 from parent-process.
> > I cann't make sure the SIGUSR1 be sended after child-process execute 
> > sigtimedwait() with 100 percent, and i try my best.
> 
> Well, in theory I suppose this could happen, but you'd have to have
> a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
> between the pipe read and signal send, while the child goes straight
> from pipe write to sigtimedwait.
> 
> Have you seen this signal be missed?  If not, then I'd rather assume
> things are reasonable.  If you have seen this happen, then why not
> instead set up a SIGUSR1 handler in the child before doing the pipe
> write, then just sleep for 3 seconds instead of doing sigtimedwait?

Thanks Serge.

Gui,

Are you planning any further patch(s) for this ?

Regards--
Subrata

> 
> > Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
> > --- testcases/kernel/containers/pidns/pidns12-old.c	2009-05-14 17:00:20.000000000 +0800
> > +++ testcases/kernel/containers/pidns/pidns12.c	2009-05-15 15:15:22.000000000 +0800
> > @@ -109,7 +109,7 @@ int child_fn(void *arg)
> >  	}
> > 
> >  	/* Set timeout for sigtimedwait */
> > -	timeout.tv_sec = 3;
> > +	timeout.tv_sec = 10;
> >  	timeout.tv_nsec = 0;
> > 
> >  	/* Set mask to wait for SIGUSR1 signal */
> > @@ -182,6 +182,9 @@ int main(int argc, char *argv[])
> >  		cleanup();
> >  	}
> > 
> > +	/*Try best to make sure the SIGUSR1 be sended after child-process execute sigtimedwait*/
> > +	sleep(5);
> > +
> >  	/* Send SIGUSR1 to container init */
> >  	if (kill(cpid, SIGUSR1) == -1) {
> >  		tst_resm(TBROK, "parent: kill() failed(%s).", strerror(errno));
> > 
> > 
> > ------------------------------------------------------------------------------
> > Crystal Reports - New Free Runtime and 30 Day Trial
> > Check out the new simplified licensing option that enables 
> > unlimited royalty-free distribution of the report engine 
> > for externally facing server and web deployment. 
> > http://p.sf.net/sfu/businessobjects
> > _______________________________________________
> > Ltp-list mailing list
> > Ltp-list@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/ltp-list
> 
> ------------------------------------------------------------------------------
> Crystal Reports - New Free Runtime and 30 Day Trial
> Check out the new simplified licensing option that enables 
> unlimited royalty-free distribution of the report engine 
> for externally facing server and web deployment. 
> http://p.sf.net/sfu/businessobjects
> _______________________________________________
> Ltp-list mailing list
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> https://lists.sourceforge.net/lists/listinfo/ltp-list


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Re: [LTP] [PATCH] Synchronization between two processes

[Serge E. Hallyn]

Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote: 
> > Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
> > > The child-process wait SIGUSR1 which would be sended by parent-process,
> > > if the child-process execute sigtimedwait() after parent-process send 
> > > the signal, it would never receive the SIGUSR1 from parent-process.
> > > I cann't make sure the SIGUSR1 be sended after child-process execute 
> > > sigtimedwait() with 100 percent, and i try my best.
> > 
> > Well, in theory I suppose this could happen, but you'd have to have
> > a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
> > between the pipe read and signal send, while the child goes straight
> > from pipe write to sigtimedwait.
> > 
> > Have you seen this signal be missed?  If not, then I'd rather assume
> > things are reasonable.  If you have seen this happen, then why not
> > instead set up a SIGUSR1 handler in the child before doing the pipe
> > write, then just sleep for 3 seconds instead of doing sigtimedwait?
> 
> Thanks Serge.

Or, if I'm being unreasonable, then at least have the parent only wait
for at most 1 second, and leave the child alone.  Every every ltp test
is going to hang for 5 seconds...

But I prefer setting the signal handler ahead of time.

> Gui,
> 
> Are you planning any further patch(s) for this ?

thanks,
-serge

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Re: [LTP] [PATCH] Synchronization between two processes

[Wei Yongjun]

Serge E. Hallyn wrote:
> Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
>   
>> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote: 
>>     
>>> Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
>>>       
>>>> The child-process wait SIGUSR1 which would be sended by parent-process,
>>>> if the child-process execute sigtimedwait() after parent-process send 
>>>> the signal, it would never receive the SIGUSR1 from parent-process.
>>>> I cann't make sure the SIGUSR1 be sended after child-process execute 
>>>> sigtimedwait() with 100 percent, and i try my best.
>>>>         
>>> Well, in theory I suppose this could happen, but you'd have to have
>>> a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
>>> between the pipe read and signal send, while the child goes straight
>>> from pipe write to sigtimedwait.
>>>
>>> Have you seen this signal be missed?  If not, then I'd rather assume
>>> things are reasonable.  If you have seen this happen, then why not
>>> instead set up a SIGUSR1 handler in the child before doing the pipe
>>> write, then just sleep for 3 seconds instead of doing sigtimedwait?
>>>       
>> Thanks Serge.
>>     
>
> Or, if I'm being unreasonable, then at least have the parent only wait
> for at most 1 second, and leave the child alone.  Every every ltp test
> is going to hang for 5 seconds...
>
> But I prefer setting the signal handler ahead of time.
>
>   
Sorry to relpy late.

As your last advice, i change the test case, and it work will.

[PATCH] fix sync problem between two processes of pidns12 test

The child-process wait SIGUSR1 which would be sended by parent-process,
if the child-process execute sigtimedwait() after parent-process send
the signal, it would never receive the SIGUSR1 from parent-process.

This patch rewrite child_signal_handler() to handle to SIGUSR1 and
instead sigtimedwait() with sleep for 3 seconds.
 
Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
---
 testcases/kernel/containers/pidns/pidns12.c |   35 ++++++--------------------
 1 files changed, 8 insertions(+), 27 deletions(-)

diff --git a/testcases/kernel/containers/pidns/pidns12.c b/testcases/kernel/containers/pidns/pidns12.c
index f893021..9120e82 100644
--- a/testcases/kernel/containers/pidns/pidns12.c
+++ b/testcases/kernel/containers/pidns/pidns12.c
@@ -72,8 +72,13 @@ void cleanup()
  */
 static void child_signal_handler(int sig, siginfo_t *si, void *unused)
 {
-	/* sigtimedwait() traps siginfo details, so this wont be called */
-	tst_resm(TWARN, "cinit: control should have not reached here!");
+	/* Recieved SIGUSR1. Check sender pid */
+	if (si->si_pid == 0)
+		tst_resm(TPASS, "cinit: signalling PID (from other namespace)"\
+				" is 0 as expected");
+	else
+		tst_resm(TFAIL, "cinit: signalling PID (from other namespace)"\
+				" is not 0, but %d.", si->si_pid);
 }
 
 /*
@@ -82,9 +87,6 @@ static void child_signal_handler(int sig, siginfo_t *si, void *unused)
 int child_fn(void *arg)
 {
 	struct sigaction sa;
-	sigset_t newset;
-	siginfo_t info;
-	struct timespec timeout;
 	pid_t pid, ppid;
 
 	/* Set process id and parent pid */
@@ -108,34 +110,13 @@ int child_fn(void *arg)
 		cleanup();
 	}
 
-	/* Set timeout for sigtimedwait */
-	timeout.tv_sec = 3;
-	timeout.tv_nsec = 0;
-
-	/* Set mask to wait for SIGUSR1 signal */
-	sigemptyset(&newset);
-	sigaddset(&newset, SIGUSR1);
-
 	/* Let parent to signal SIGUSR1 */
 	if (write(pipefd[1], "c:go\0", 5) != 5) {
 		tst_resm(TBROK, "cinit: pipe is broken to write");
 		cleanup();
 	}
 
-	/* Wait for SIGUSR1 */
-	if (sigtimedwait(&newset, &info, &timeout) != SIGUSR1) {
-		tst_resm(TBROK, "cinit: sigtimedwait() failed(%s).",
-				strerror(errno));
-		cleanup();
-	}
-
-	/* Recieved SIGUSR1. Check sender pid */
-	if (info.si_pid == 0)
-		tst_resm(TPASS, "cinit: signalling PID (from other namespace)"\
-				" is 0 as expected");
-	else
-		tst_resm(TFAIL, "cinit: signalling PID (from other namespace)"\
-				" is not 0, but %d.", info.si_pid);
+	sleep(3);
 
 	/* cleanup and exit */
 	close(pipefd[1]);
-- 
1.6.3




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Re: [LTP] [PATCH] Synchronization between two processes

[Subrata Modak]

On Fri, 2009-05-22 at 13:55 +0800, Wei Yongjun wrote: 
> Serge E. Hallyn wrote:
> > Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
> >   
> >> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote: 
> >>     
> >>> Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
> >>>       
> >>>> The child-process wait SIGUSR1 which would be sended by parent-process,
> >>>> if the child-process execute sigtimedwait() after parent-process send 
> >>>> the signal, it would never receive the SIGUSR1 from parent-process.
> >>>> I cann't make sure the SIGUSR1 be sended after child-process execute 
> >>>> sigtimedwait() with 100 percent, and i try my best.
> >>>>         
> >>> Well, in theory I suppose this could happen, but you'd have to have
> >>> a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
> >>> between the pipe read and signal send, while the child goes straight
> >>> from pipe write to sigtimedwait.
> >>>
> >>> Have you seen this signal be missed?  If not, then I'd rather assume
> >>> things are reasonable.  If you have seen this happen, then why not
> >>> instead set up a SIGUSR1 handler in the child before doing the pipe
> >>> write, then just sleep for 3 seconds instead of doing sigtimedwait?
> >>>       
> >> Thanks Serge.
> >>     
> >
> > Or, if I'm being unreasonable, then at least have the parent only wait
> > for at most 1 second, and leave the child alone.  Every every ltp test
> > is going to hang for 5 seconds...
> >
> > But I prefer setting the signal handler ahead of time.
> >
> >   
> Sorry to relpy late.
> 
> As your last advice, i change the test case, and it work will.
> 
> [PATCH] fix sync problem between two processes of pidns12 test
> 
> The child-process wait SIGUSR1 which would be sended by parent-process,
> if the child-process execute sigtimedwait() after parent-process send
> the signal, it would never receive the SIGUSR1 from parent-process.
> 
> This patch rewrite child_signal_handler() to handle to SIGUSR1 and
> instead sigtimedwait() with sleep for 3 seconds.
> 
> Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>

Serge,

Your view on this new solution ?

Regards--
Subrata

> ---
>  testcases/kernel/containers/pidns/pidns12.c |   35 ++++++--------------------
>  1 files changed, 8 insertions(+), 27 deletions(-)
> 
> diff --git a/testcases/kernel/containers/pidns/pidns12.c b/testcases/kernel/containers/pidns/pidns12.c
> index f893021..9120e82 100644
> --- a/testcases/kernel/containers/pidns/pidns12.c
> +++ b/testcases/kernel/containers/pidns/pidns12.c
> @@ -72,8 +72,13 @@ void cleanup()
>   */
>  static void child_signal_handler(int sig, siginfo_t *si, void *unused)
>  {
> -	/* sigtimedwait() traps siginfo details, so this wont be called */
> -	tst_resm(TWARN, "cinit: control should have not reached here!");
> +	/* Recieved SIGUSR1. Check sender pid */
> +	if (si->si_pid == 0)
> +		tst_resm(TPASS, "cinit: signalling PID (from other namespace)"\
> +				" is 0 as expected");
> +	else
> +		tst_resm(TFAIL, "cinit: signalling PID (from other namespace)"\
> +				" is not 0, but %d.", si->si_pid);
>  }
> 
>  /*
> @@ -82,9 +87,6 @@ static void child_signal_handler(int sig, siginfo_t *si, void *unused)
>  int child_fn(void *arg)
>  {
>  	struct sigaction sa;
> -	sigset_t newset;
> -	siginfo_t info;
> -	struct timespec timeout;
>  	pid_t pid, ppid;
> 
>  	/* Set process id and parent pid */
> @@ -108,34 +110,13 @@ int child_fn(void *arg)
>  		cleanup();
>  	}
> 
> -	/* Set timeout for sigtimedwait */
> -	timeout.tv_sec = 3;
> -	timeout.tv_nsec = 0;
> -
> -	/* Set mask to wait for SIGUSR1 signal */
> -	sigemptyset(&newset);
> -	sigaddset(&newset, SIGUSR1);
> -
>  	/* Let parent to signal SIGUSR1 */
>  	if (write(pipefd[1], "c:go\0", 5) != 5) {
>  		tst_resm(TBROK, "cinit: pipe is broken to write");
>  		cleanup();
>  	}
> 
> -	/* Wait for SIGUSR1 */
> -	if (sigtimedwait(&newset, &info, &timeout) != SIGUSR1) {
> -		tst_resm(TBROK, "cinit: sigtimedwait() failed(%s).",
> -				strerror(errno));
> -		cleanup();
> -	}
> -
> -	/* Recieved SIGUSR1. Check sender pid */
> -	if (info.si_pid == 0)
> -		tst_resm(TPASS, "cinit: signalling PID (from other namespace)"\
> -				" is 0 as expected");
> -	else
> -		tst_resm(TFAIL, "cinit: signalling PID (from other namespace)"\
> -				" is not 0, but %d.", info.si_pid);
> +	sleep(3);
> 
>  	/* cleanup and exit */
>  	close(pipefd[1]);


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Re: [LTP] [PATCH] Synchronization between two processes

[Serge E. Hallyn]

Quoting Wei Yongjun (yjwei@cn.fujitsu.com):
> Serge E. Hallyn wrote:
>> Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
>>   
>>> On Fri, 2009-05-15 at 08:45 -0500, Serge E. Hallyn wrote:     
>>>> Quoting Gui Xiaohua (guixh@cn.fujitsu.com):
>>>>       
>>>>> The child-process wait SIGUSR1 which would be sended by parent-process,
>>>>> if the child-process execute sigtimedwait() after parent-process 
>>>>> send the signal, it would never receive the SIGUSR1 from 
>>>>> parent-process.
>>>>> I cann't make sure the SIGUSR1 be sended after child-process 
>>>>> execute sigtimedwait() with 100 percent, and i try my best.
>>>>>         
>>>> Well, in theory I suppose this could happen, but you'd have to have
>>>> a pretty bad scheduler if the parent can do a strcmp(buf, "c:go")
>>>> between the pipe read and signal send, while the child goes straight
>>>> from pipe write to sigtimedwait.
>>>>
>>>> Have you seen this signal be missed?  If not, then I'd rather assume
>>>> things are reasonable.  If you have seen this happen, then why not
>>>> instead set up a SIGUSR1 handler in the child before doing the pipe
>>>> write, then just sleep for 3 seconds instead of doing sigtimedwait?
>>>>       
>>> Thanks Serge.
>>>     
>>
>> Or, if I'm being unreasonable, then at least have the parent only wait
>> for at most 1 second, and leave the child alone.  Every every ltp test
>> is going to hang for 5 seconds...
>>
>> But I prefer setting the signal handler ahead of time.
>>
>>   
> Sorry to relpy late.
>
> As your last advice, i change the test case, and it work will.
>
> [PATCH] fix sync problem between two processes of pidns12 test
>
> The child-process wait SIGUSR1 which would be sended by parent-process,
> if the child-process execute sigtimedwait() after parent-process send
> the signal, it would never receive the SIGUSR1 from parent-process.
>
> This patch rewrite child_signal_handler() to handle to SIGUSR1 and
> instead sigtimedwait() with sleep for 3 seconds.

Thank you, this looks right.

I assume the reason it wasn't originally done this way, was out of
a concern that the TPASS/TFAIL out of signal handler wouldn't
count...

-serge

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Re: [LTP] [PATCH] Synchronization between two processes

[Serge E. Hallyn]

Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
> > Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
> 
> Serge,
> 
> Your view on this new solution ?

Oops, i forgot to officially note:

Acked-by: Serge Hallyn <serue@us.ibm.com>

thanks,
-serge

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Re: [LTP] [PATCH] Synchronization between two processes

[Subrata Modak]

On Mon, 2009-05-25 at 17:17 -0500, Serge E. Hallyn wrote: 
> Quoting Subrata Modak (subrata@linux.vnet.ibm.com):
> > > Signed-off-by: Gui Xiaohua <guixh@cn.fujitsu.com>
> > 
> > Serge,
> > 
> > Your view on this new solution ?
> 
> Oops, i forgot to officially note:
> 
> Acked-by: Serge Hallyn <serue@us.ibm.com>

Thanks to both of you.

Regards--
Subrata

> 
> thanks,
> -serge


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