[LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[Peng Haitao]

commit d2e9f84 replace fprintf() with snprintf() in tst_print(), but this will
cause container_test.sh hang in case shmem_2nstest.

If compile tst_res.c without -O[level], the case will not hang.

When I test the following cases:
# ./shmem_2nstest none
shmem_2nstest    0  TINFO  :  Shared Memory namespace test : none
shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
shmem_2nstest    1  TPASS  :  Plain cloned process able to access shmem segment created
# ./shmem_2nstest unshare
shmem_2nstest    0  TINFO  :  Shared Memory namespace test : unshare
shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
shmem_2nstest    0  TINFO  :  Cont2: Able to allocate shmem seg with the same key
shmem_2nstest    1  TPASS  :  unshare : In namespace2 unable to access the shmem seg created in Namespace1
# ./shmem_2nstest clone
shmem_2nstest    0  TINFO  :  Shared Memory namespace test : clone

this will hang up.

So I think tst_resm("Cont1") will cause hang.

Signed-off-by: Peng Haitao <penght@cn.fujitsu.com>
---
 .../kernel/containers/sysvipc/shmem_2nstest.c      |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/testcases/kernel/containers/sysvipc/shmem_2nstest.c b/testcases/kernel/containers/sysvipc/shmem_2nstest.c
index 7a468ad..28e91ff 100644
--- a/testcases/kernel/containers/sysvipc/shmem_2nstest.c
+++ b/testcases/kernel/containers/sysvipc/shmem_2nstest.c
@@ -69,8 +69,8 @@ int check_shmem1(void *vtest)
 	if (id1 == -1)
 		tst_brkm(TFAIL|TERRNO, NULL, "shmget failed");
 
-	tst_resm(TINFO, "Cont1: Able to create shared mem segment");
 	write(p1[1], "done", 5);
+	tst_resm(TINFO, "Cont1: Able to create shared mem segment");
 	tst_exit();
 }
 
-- 
1.7.1

-- 
Best Regards,
Peng


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Re: [LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[Wanlong Gao]

On 02/21/2012 01:43 PM, Peng Haitao wrote:

> 
> commit d2e9f84 replace fprintf() with snprintf() in tst_print(), but this will
> cause container_test.sh hang in case shmem_2nstest.
> 
> If compile tst_res.c without -O[level], the case will not hang.
> 
> When I test the following cases:
> # ./shmem_2nstest none
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : none
> shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
> shmem_2nstest    1  TPASS  :  Plain cloned process able to access shmem segment created
> # ./shmem_2nstest unshare
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : unshare
> shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
> shmem_2nstest    0  TINFO  :  Cont2: Able to allocate shmem seg with the same key
> shmem_2nstest    1  TPASS  :  unshare : In namespace2 unable to access the shmem seg created in Namespace1
> # ./shmem_2nstest clone
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : clone
> 
> this will hang up.
> 
> So I think tst_resm("Cont1") will cause hang.


Tested OK to me. 

Acked-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>

> 
> Signed-off-by: Peng Haitao <penght@cn.fujitsu.com>
> ---
>  .../kernel/containers/sysvipc/shmem_2nstest.c      |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/testcases/kernel/containers/sysvipc/shmem_2nstest.c b/testcases/kernel/containers/sysvipc/shmem_2nstest.c
> index 7a468ad..28e91ff 100644
> --- a/testcases/kernel/containers/sysvipc/shmem_2nstest.c
> +++ b/testcases/kernel/containers/sysvipc/shmem_2nstest.c
> @@ -69,8 +69,8 @@ int check_shmem1(void *vtest)
>  	if (id1 == -1)
>  		tst_brkm(TFAIL|TERRNO, NULL, "shmget failed");
>  
> -	tst_resm(TINFO, "Cont1: Able to create shared mem segment");
>  	write(p1[1], "done", 5);
> +	tst_resm(TINFO, "Cont1: Able to create shared mem segment");
>  	tst_exit();
>  }
>  



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Re: [LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[Cyril Hrubis]

Hi!
> commit d2e9f84 replace fprintf() with snprintf() in tst_print(), but this will
> cause container_test.sh hang in case shmem_2nstest.
> 
> If compile tst_res.c without -O[level], the case will not hang.
> 
> When I test the following cases:
> # ./shmem_2nstest none
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : none
> shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
> shmem_2nstest    1  TPASS  :  Plain cloned process able to access shmem segment created
> # ./shmem_2nstest unshare
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : unshare
> shmem_2nstest    0  TINFO  :  Cont1: Able to create shared mem segment
> shmem_2nstest    0  TINFO  :  Cont2: Able to allocate shmem seg with the same key
> shmem_2nstest    1  TPASS  :  unshare : In namespace2 unable to access the shmem seg created in Namespace1
> # ./shmem_2nstest clone
> shmem_2nstest    0  TINFO  :  Shared Memory namespace test : clone
> 
> this will hang up.
> 
> So I think tst_resm("Cont1") will cause hang.

Looked in the code, the stack for cloned process is four pages in size
(see ltp_clone_quick()). And when the tst_resm() is called, the buffer
created on stack to store the message most likely overflows the stack
which results in hang in snprintf(). So I would rather remove this
tst_resm() entirely.

Anyway this is good catch, thanks.

-- 
Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[Cyril Hrubis]

Hi!
> Looked in the code, the stack for cloned process is four pages in size
> (see ltp_clone_quick()). And when the tst_resm() is called, the buffer
> created on stack to store the message most likely overflows the stack
> which results in hang in snprintf(). So I would rather remove this
> tst_resm() entirely.

Hmm, or we could add a page or two to the ltp_clone_quick(), which
should be quite safe...

-- 
Cyril Hrubis
chrubis@suse.cz

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Virtualization & Cloud Management Using Capacity Planning
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also focuses on allowing computing to be delivered as a service.
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Re: [LTP] [PATCH v3 2/2] shmem_2nstest: fix a bug of hang

[Cyril Hrubis]

Hi!
> Hmm, or we could add a page or two to the ltp_clone_quick(), which
> should be quite safe...

I've commited a patch that increases the cloned process stack size from
four to six pages (which seems to be enough to work here). Please test
that this works also for you and if that change hasn't breaked anything
else.

-- 
Cyril Hrubis
chrubis@suse.cz

------------------------------------------------------------------------------
Virtualization & Cloud Management Using Capacity Planning
Cloud computing makes use of virtualization - but cloud computing 
also focuses on allowing computing to be delivered as a service.
http://www.accelacomm.com/jaw/sfnl/114/51521223/
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