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Remove the signal-waiting logic from create_sig_proc()

PATCH In review Jiri Palecek 2 participants 2 messages Jun 8, 2009 – Jun 9, 2009

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Jiri Palecek

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#0 lore raw

PATCH 1/1 Remove the signal-waiting logic from create_sig_proc()

In create_sig_proc, the child process waits for the parent to wake it with a signal. This doesn't actually solve anything, and the implementation with pause() syscall is inherently racy (the race results in a deadlock). This patch removes it; it doesn't make the function race-free (it's possible the child will send the signal before the parent had chance to run), but this is the best you can get.

Regards
Jiri Palecek

Signed-off-by Jiri Palecek <[email protected]>
---
 testcases/kernel/syscalls/utils/common_j_h.c |   10 ----------
 1 files changed, 0 insertions(+), 10 deletions(-)
testcases/kernel/syscalls/utils/common_j_h.c +0 -10
index cda3198..d122ff9 100644
@@ -102,23 +102,14 @@ int cleanup_euid(uid_t old_uid)
 /*
  * Generate a child process which will send a signal
  */
-static void sighandler_for_sig_proc(int sig)
-{
-	if (sig == SIGUSR2)
-		return;
-	return;
-}
-
 pid_t create_sig_proc(unsigned long usec, int sig)
 {
 	pid_t pid, cpid;
 
-	signal(SIGUSR2, sighandler_for_sig_proc);
 	pid = getpid();
 	cpid = fork();
 	switch (cpid) {
 	case 0:
-		pause();
 		usleep(usec);
 		kill(pid, sig);
 		_exit(0);

@@ -127,7 +118,6 @@ pid_t create_sig_proc(unsigned long usec, int sig)
 		EPRINTF("fork failed.\n");
 		return cpid;
 	default:
-		kill(cpid, SIGUSR2);
 		return cpid;
 	}
 }
Signature · 13 lines
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#1 lore raw
Quoted 8 lines · Jiri Palecek

In create_sig_proc, the child process waits for the parent to wake it
with a signal. This doesn't actually solve anything, and the implementation with pause() syscall is inherently racy (the race results in a deadlock). This patch removes it; it doesn't make the function race-free (it's possible the child will send the signal before the parent had chance to run), but this is the best you can get.

Quoted 4 lines

Regards
Jiri Palecek

Signed-off-by Jiri Palecek <[email protected]>

Thanks.

Regards--
Subrata

Quoted 33 lines
---
 testcases/kernel/syscalls/utils/common_j_h.c |   10 ----------
 1 files changed, 0 insertions(+), 10 deletions(-)
testcases/kernel/syscalls/utils/common_j_h.c +0 -9
index cda3198..d122ff9 100644
@@ -102,23 +102,14 @@ int cleanup_euid(uid_t old_uid)
 /*
  * Generate a child process which will send a signal
  */
-static void sighandler_for_sig_proc(int sig)
-{
-	if (sig == SIGUSR2)
-		return;
-	return;
-}
-
 pid_t create_sig_proc(unsigned long usec, int sig)
 {
 	pid_t pid, cpid;
 
-	signal(SIGUSR2, sighandler_for_sig_proc);
 	pid = getpid();
 	cpid = fork();
 	switch (cpid) {
 	case 0:
-		pause();
 		usleep(usec);
 		kill(pid, sig);
 		_exit(0);

testcases/kernel/syscalls/utils/common_j_h.c pid_t create_sig_proc(unsigned long usec, int sig) · line 123

Quoted 7 lines
testcases/kernel/syscalls/utils/common_j_h.c +0 -1
@@ -127,7 +118,6 @@ pid_t create_sig_proc(unsigned long usec, int sig)
 		EPRINTF("fork failed.\n");
 		return cpid;
 	default:
-		kill(cpid, SIGUSR2);
 		return cpid;
 	}
 }

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