[PATCH] powerpc/selftests: Avoid backgroud process/threads

[PATCH] powerpc/selftests: Avoid backgroud process/threads

[Breno Leitao]

Current tm-unavailable test runs for a long period (>120 seconds), and if it is
interrupted, as pressing CRTL-C (SIGINT), the foreground process (harness) dies
but the child process and threads continue to execute (with PPID = 1 now).

In this case, you'd think the test is gone, but there are two threads being
executed in background, one of the thread ('pong') consumes 100% of the CPU and
the other one ('ping') dumps output message, from time to time, in the STDOUT,
which is annoying.

This patch simply gets the child process to be SIGTERMed when the parent dies.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>
---
 tools/testing/selftests/powerpc/tm/tm-unavailable.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/powerpc/tm/tm-unavailable.c b/tools/testing/selftests/powerpc/tm/tm-unavailable.c
index 156c8e750259..c42f8b60063c 100644
--- a/tools/testing/selftests/powerpc/tm/tm-unavailable.c
+++ b/tools/testing/selftests/powerpc/tm/tm-unavailable.c
@@ -23,6 +23,8 @@
 #include <stdbool.h>
 #include <pthread.h>
 #include <sched.h>
+#include <signal.h>
+#include <sys/prctl.h>
 
 #include "tm.h"
 
@@ -342,6 +344,9 @@ int tm_unavailable_test(void)
 
 	SKIP_IF(!have_htm());
 
+	/* Send me SIGTERM if PPID is dead (as SIGINTed) */
+	prctl(PR_SET_PDEATHSIG, SIGTERM);
+
 	/* Set only CPU 0 in the mask. Both threads will be bound to CPU 0. */
 	CPU_ZERO(&cpuset);
 	CPU_SET(0, &cpuset);
-- 
2.16.3

Re: [PATCH] powerpc/selftests: Avoid backgroud process/threads

[Michael Ellerman]

Breno Leitao <leitao@debian.org> writes:

> Current tm-unavailable test runs for a long period (>120 seconds), and if it is
> interrupted, as pressing CRTL-C (SIGINT), the foreground process (harness) dies
> but the child process and threads continue to execute (with PPID = 1 now).
>
> In this case, you'd think the test is gone, but there are two threads being
> executed in background, one of the thread ('pong') consumes 100% of the CPU and
> the other one ('ping') dumps output message, from time to time, in the STDOUT,
> which is annoying.
>
> This patch simply gets the child process to be SIGTERMed when the parent dies.

Hmm, I think we should fix this in the harness if possible.

In run_test() it does:

	/* Kill anything else in the process group that is still running */
	kill(-pid, SIGTERM);


But that doesn't work if the harness has been killed with Ctrl-C.

I think the harness could have a SIGINT handler that basically does the
above and then exits?

cheers

[PATCH v2] selftests/powerpc: Avoid remaining process/threads

[Breno Leitao]

There are some powerpc selftests, as tm/tm-unavailable, that run for a long
period (>120 seconds), and if it is interrupted, as pressing CRTL-C
(SIGINT), the foreground process (harness) dies but the child process and
threads continue to execute (with PPID = 1 now) in background.

In this case, you'd think the whole test exited, but there are remaining
threads and processes being executed in background. Sometimes these
zoombies processes are doing annoying things, as consuming the whole CPU or
dumping things to STDOUT.

This patch fixes this problem by creating a SIGINT handler in the harness
process, which will kill the child process group once a SIGINT is caught.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>
---
 tools/testing/selftests/powerpc/harness.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
index 66d31de60b9a..06c51e8d8ccb 100644
--- a/tools/testing/selftests/powerpc/harness.c
+++ b/tools/testing/selftests/powerpc/harness.c
@@ -22,12 +22,12 @@
 #define KILL_TIMEOUT	5
 
 static uint64_t timeout = 120;
+pid_t pid;
 
 int run_test(int (test_function)(void), char *name)
 {
 	bool terminated;
 	int rc, status;
-	pid_t pid;
 
 	/* Make sure output is flushed before forking */
 	fflush(stdout);
@@ -85,13 +85,16 @@ int run_test(int (test_function)(void), char *name)
 	return status;
 }
 
-static void alarm_handler(int signum)
+static void sig_handler(int signum)
 {
-	/* Jut wake us up from waitpid */
+	if (signum == SIGINT)
+		kill(-pid, SIGTERM);
+
+	/* if SIGALRM, just wake us up from waitpid */
 }
 
-static struct sigaction alarm_action = {
-	.sa_handler = alarm_handler,
+static struct sigaction sig_action = {
+	.sa_handler = sig_handler,
 };
 
 void test_harness_set_timeout(uint64_t time)
@@ -106,8 +109,14 @@ int test_harness(int (test_function)(void), char *name)
 	test_start(name);
 	test_set_git_version(GIT_VERSION);
 
-	if (sigaction(SIGALRM, &alarm_action, NULL)) {
-		perror("sigaction");
+	if (sigaction(SIGINT, &sig_action, NULL)) {
+		perror("sigaction (sigint)");
+		test_error(name);
+		return 1;
+	}
+
+	if (sigaction(SIGALRM, &sig_action, NULL)) {
+		perror("sigaction (sigalrm)");
 		test_error(name);
 		return 1;
 	}
-- 
2.16.3

Re: [PATCH v2] selftests/powerpc: Avoid remaining process/threads

[Michael Ellerman]

Breno Leitao <leitao@debian.org> writes:

> diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
> index 66d31de60b9a..06c51e8d8ccb 100644
> --- a/tools/testing/selftests/powerpc/harness.c
> +++ b/tools/testing/selftests/powerpc/harness.c
> @@ -85,13 +85,16 @@ int run_test(int (test_function)(void), char *name)
>  	return status;
>  }
>  
> -static void alarm_handler(int signum)
> +static void sig_handler(int signum)
>  {
> -	/* Jut wake us up from waitpid */
> +	if (signum == SIGINT)
> +		kill(-pid, SIGTERM);

I don't think we need to do that here, if we just return then we'll pop
out of the waitpid() and go via the normal path.

Can you test with the existing signal handler, but wired up to SIGINT?

cheers

Re: [PATCH v2] selftests/powerpc: Avoid remaining process/threads

[Breno Leitao]

Hello Michael,

On 08/06/2018 08:06 AM, Michael Ellerman wrote:
> Breno Leitao <leitao@debian.org> writes:
> 
>> diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
>> index 66d31de60b9a..06c51e8d8ccb 100644
>> --- a/tools/testing/selftests/powerpc/harness.c
>> +++ b/tools/testing/selftests/powerpc/harness.c
>> @@ -85,13 +85,16 @@ int run_test(int (test_function)(void), char *name)
>>  	return status;
>>  }
>>  
>> -static void alarm_handler(int signum)
>> +static void sig_handler(int signum)
>>  {
>> -	/* Jut wake us up from waitpid */
>> +	if (signum == SIGINT)
>> +		kill(-pid, SIGTERM);
> 
> I don't think we need to do that here, if we just return then we'll pop
> out of the waitpid() and go via the normal path.

Correct, if we press ^C while the parent process is waiting at waitpid(),
then waitpid() syscall will be interrupted (EINTR) and never restarted again
(unless we set sa_flags = SA_RESTART), thus, the code will restart to execute
the next instruction when the signal handler is done, as we had skipped
waitpid().

>From a theoretical point of view, the user can press ^C before the process
executes waitpid() syscall. In this case and the process will not 'skip' the
waitpid(), which will continue to wait. We can clearly force this behavior
putting a sleep(1) before waitpid() and pressing  ^C in the very first
second, it will 'skip' the nanosleep() syscall instead of waitpid() which
will be there, and the ^C will be ignored (thus not calling kill(-pid, SIGTERM)).

>From a practical point of view, I will prepare a v3 patch. :-)

[PATCH v3] selftests/powerpc: Kill child processes on SIGINT

[Breno Leitao]

There are some powerpc selftests, as tm/tm-unavailable, that run for a long
period (>120 seconds), and if it is interrupted, as pressing CRTL-C
(SIGINT), the foreground process (harness) dies but the child process and
threads continue to execute (with PPID = 1 now) in background.

In this case, you'd think the whole test exited, but there are remaining
threads and processes being executed in background. Sometimes these
zombies processes are doing annoying things, as consuming the whole CPU or
dumping things to STDOUT.

This patch fixes this problem by attaching an empty signal handler to
SIGINT in the harness process. This handler will interrupt (EINTR) the
parent process waitpid() call, letting the code to follow through the
normal flow, which will kill all the processes in the child process group.

This patch also fixes a typo.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>
---
 tools/testing/selftests/powerpc/harness.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
index 66d31de60b9a..9d7166dfad1e 100644
--- a/tools/testing/selftests/powerpc/harness.c
+++ b/tools/testing/selftests/powerpc/harness.c
@@ -85,13 +85,13 @@ int run_test(int (test_function)(void), char *name)
 	return status;
 }
 
-static void alarm_handler(int signum)
+static void sig_handler(int signum)
 {
-	/* Jut wake us up from waitpid */
+	/* Just wake us up from waitpid */
 }
 
-static struct sigaction alarm_action = {
-	.sa_handler = alarm_handler,
+static struct sigaction sig_action = {
+	.sa_handler = sig_handler,
 };
 
 void test_harness_set_timeout(uint64_t time)
@@ -106,8 +106,14 @@ int test_harness(int (test_function)(void), char *name)
 	test_start(name);
 	test_set_git_version(GIT_VERSION);
 
-	if (sigaction(SIGALRM, &alarm_action, NULL)) {
-		perror("sigaction");
+	if (sigaction(SIGINT, &sig_action, NULL)) {
+		perror("sigaction (sigint)");
+		test_error(name);
+		return 1;
+	}
+
+	if (sigaction(SIGALRM, &sig_action, NULL)) {
+		perror("sigaction (sigalrm)");
 		test_error(name);
 		return 1;
 	}
-- 
2.16.3

Re: [v3] selftests/powerpc: Kill child processes on SIGINT

[Michael Ellerman]

On Tue, 2018-08-07 at 14:15:39 UTC, Breno Leitao wrote:
> There are some powerpc selftests, as tm/tm-unavailable, that run for a long
> period (>120 seconds), and if it is interrupted, as pressing CRTL-C
> (SIGINT), the foreground process (harness) dies but the child process and
> threads continue to execute (with PPID = 1 now) in background.
> 
> In this case, you'd think the whole test exited, but there are remaining
> threads and processes being executed in background. Sometimes these
> zombies processes are doing annoying things, as consuming the whole CPU or
> dumping things to STDOUT.
> 
> This patch fixes this problem by attaching an empty signal handler to
> SIGINT in the harness process. This handler will interrupt (EINTR) the
> parent process waitpid() call, letting the code to follow through the
> normal flow, which will kill all the processes in the child process group.
> 
> This patch also fixes a typo.
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/7c27a26e1ed5a7dd709aa19685d2c9

cheers

Re: [PATCH v2] selftests/powerpc: Avoid remaining process/threads

[Michael Ellerman]

Breno Leitao <leitao@debian.org> writes:

> Hello Michael,
>
> On 08/06/2018 08:06 AM, Michael Ellerman wrote:
>> Breno Leitao <leitao@debian.org> writes:
>> 
>>> diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
>>> index 66d31de60b9a..06c51e8d8ccb 100644
>>> --- a/tools/testing/selftests/powerpc/harness.c
>>> +++ b/tools/testing/selftests/powerpc/harness.c
>>> @@ -85,13 +85,16 @@ int run_test(int (test_function)(void), char *name)
>>>  	return status;
>>>  }
>>>  
>>> -static void alarm_handler(int signum)
>>> +static void sig_handler(int signum)
>>>  {
>>> -	/* Jut wake us up from waitpid */
>>> +	if (signum == SIGINT)
>>> +		kill(-pid, SIGTERM);
>> 
>> I don't think we need to do that here, if we just return then we'll pop
>> out of the waitpid() and go via the normal path.
>
> Correct, if we press ^C while the parent process is waiting at waitpid(),
> then waitpid() syscall will be interrupted (EINTR) and never restarted again
> (unless we set sa_flags = SA_RESTART), thus, the code will restart to execute
> the next instruction when the signal handler is done, as we had skipped
> waitpid().
>
> From a theoretical point of view, the user can press ^C before the process
> executes waitpid() syscall. In this case and the process will not 'skip' the
> waitpid(), which will continue to wait. We can clearly force this behavior
> putting a sleep(1) before waitpid() and pressing  ^C in the very first
> second, it will 'skip' the nanosleep() syscall instead of waitpid() which
> will be there, and the ^C will be ignored (thus not calling kill(-pid, SIGTERM)).

True.

Though that race also exists vs us registering the SIGINT handler, so
it's basically not solvable, the user can always press ^C before we're
ready.

cheers