为什么不从子进程中获取退出状态? [英] Why aren't I picking up the exit status from my child process?
问题描述
我有一个正在管理的Perl程序，该程序能够派生多个进程(达到指定的限制)，监视它们，并在它们退出时，派生其他进程(再次，直到限制)，直到要运行的事物列表完成为止.它工作正常，但出于某种原因似乎无法从我的子进程中获取正确的退出状态.
无效的代码使用Perl的fork()，waitpid()，子进程使用POSIX::_exit()退出.以下是相关代码的摘录:
叉形代码:
# Initialize process if running in parallel mode
my $pid;
if ($options{'parallel'} > 0) {
log_status("Waiting to fork test #".$curr_test{'id'}."...\n");
# Here, wait for child processes to complete so we can fork off new ones without going over the specified limit
while ( keys(%children) >= $options{'parallel'}) {
my $kid = waitpid(-1, 0);
my $kid_status = $?;
if ($kid > 0) {
log_status("Child process (PID ".$kid.", test ".$children{$kid}.") exited with status ".$kid_status.".\n");
$error_status |= $kid_status;
delete $children{$kid};
}
}
$pid = fork();
tdie("Unable to fork!\n") unless defined $pid;
if ($pid != 0) {
# I'm the parent
$is_child = 0;
log_status("Forked child process (PID ".$pid.").\n");
$children{$pid} = $curr_test{'logstr'};
next TEST_LOOP;
}
else {
# I'm the child
$is_child = 1;
log_status("Starting test = ".$curr_test{'logstr'}."\n");
}
}
退出子进程代码:
### finish_child() ###
# Handles exiting the script, like the finish() function, but only when running as a child process in parallel mode.
# Parameters:
# - The error code to exit with
###
sub finish_child( $ ) {
my ($error_status) = @_;
# If running in parallel mode, exit this fork
if ($options{'parallel'} > 0) {
log_status("Entering: ".Cwd::abs_path("..")."\n");
chdir "..";
log_status("Exiting with status: ".$error_status."\n");
POSIX::_exit($error_status);
}
}
在我的示例运行中，在此处调用finish_child()的地方:
# If build failed, log status and gracefully clean up logfiles, then continue to next test in list.
if ($test_status > 0) {
$email_subject = "Build failed!";
log_status("Build of ".$testline." FAILED.\n");
tlog(1, "Build of ".$testline." FAILED.\n");
log_status("Entering: ".Cwd::abs_path("..")."\n");
chdir "..";
log_report(\%curr_test, $test_status);
# Print out pass/fail status for each test as it completes
$quietmode = $options{'quiet'}; # Backup quiet mode setting
$options{'quiet'} = 0;
if ($test_status == 0) {
log_status("Test ".$testline." PASSED.\n");
tlog(0, "Test ".$testline." PASSED.\n");
}
else {
log_status("Test ".$testline." FAILED.\n");
tlog(1, "Test ".$testline." FAILED.\n");
}
$options{'quiet'} = $quietmode; # Restore quiet mode setting
finish_logs();
# Link logs to global area and rename if running multiple tests
system("ln -sf ".$root_dir."/verify/".$curr_test{'id'}."/".$verify::logfile." ../".(($test_status > 0) ? "fail".$curr_test{'id'}.".log" : "pass".$curr_test{'id'}.".log" )) if (@tests > 1);
if ($options{'parallel'} > 0 && $pid == 0) {
# If we're in parallel mode and I'm a child process, I should exit, instead of continuing to loop.
finish_child($test_status);
}
else {
# If we're not in parallel mode, I should continue to loop.
next TEST_LOOP;
}
}
这是根据我执行的运行记录看到的行为:
<Parent> Waiting for all child processes to complete...
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Running user command: make --directory <trimmed> TARGET=build BUILD_DIR=<trimmed> RUN_DIR=<trimmed>
<Child> [PID 28657] User command finished with return code: 512
<Child> [PID 28657] Build step finished with return code 512
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Build of rx::basic(1) FAILED.
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Test rx::basic(1) FAILED.
<Child> [PID 28657] Closing log file.
<Child> [PID 28657] Closing error log file.
<Child> [PID 28657] Entering: <trimmed>
<Parent> Child process (PID 28657, test rx::basic(1)) exited with status 0.
我有使用Perl IPC运行命令的代码(代替system()调用)，以获得更大的灵活性，可以正确地选择退出代码，您可以在日志文件的用户命令"行中看到该代码.
在这里我可能做错了什么?在这种情况下，为什么我不能从$?获取退出状态?我在网上找到的示例似乎都表明这应该可以正常工作.
作为参考，我正在运行Perl v5.10.1.如果您觉得需要查看其余的代码，则此Perl工具也是GitHub上的开源代码: https://github.com/benrichards86/Verify/blob/master/verify.pl
如果$test_status为512，您是否呼叫POSIX::_exit(512)?那是不对的.
子进程应该调用POSIX::_exit，其操作数的范围为0到255，而获得该子进程的Perl父进程将把$?设置为 exit-status << 8.. >
POSIX::_exit(512)等效于POSIX::_exit(512 % 256)或POSIX::_exit(0).
I have a Perl program that I'm managing on that has the ability to fork off multiple processes (up to a specified limit), monitor them, and as they exit, fork off additional processes (once again, up to the limit), until the list of things to run is completed. It works fine, except for some reason it doesn't appear to be picking up the correct exit status from my child processes.
The code that doesn't work uses Perl's fork(), waitpid(), and the child processes use POSIX::_exit() to quit. Here's some excerpts of the relevant code:
Forking code:
# Initialize process if running in parallel mode
my $pid;
if ($options{'parallel'} > 0) {
log_status("Waiting to fork test #".$curr_test{'id'}."...\n");
# Here, wait for child processes to complete so we can fork off new ones without going over the specified limit
while ( keys(%children) >= $options{'parallel'}) {
my $kid = waitpid(-1, 0);
my $kid_status = $?;
if ($kid > 0) {
log_status("Child process (PID ".$kid.", test ".$children{$kid}.") exited with status ".$kid_status.".\n");
$error_status |= $kid_status;
delete $children{$kid};
}
}
$pid = fork();
tdie("Unable to fork!\n") unless defined $pid;
if ($pid != 0) {
# I'm the parent
$is_child = 0;
log_status("Forked child process (PID ".$pid.").\n");
$children{$pid} = $curr_test{'logstr'};
next TEST_LOOP;
}
else {
# I'm the child
$is_child = 1;
log_status("Starting test = ".$curr_test{'logstr'}."\n");
}
}
Exit child process code:
### finish_child() ###
# Handles exiting the script, like the finish() function, but only when running as a child process in parallel mode.
# Parameters:
# - The error code to exit with
###
sub finish_child( $ ) {
my ($error_status) = @_;
# If running in parallel mode, exit this fork
if ($options{'parallel'} > 0) {
log_status("Entering: ".Cwd::abs_path("..")."\n");
chdir "..";
log_status("Exiting with status: ".$error_status."\n");
POSIX::_exit($error_status);
}
}
Here's where finish_child() is called in my example run:
# If build failed, log status and gracefully clean up logfiles, then continue to next test in list.
if ($test_status > 0) {
$email_subject = "Build failed!";
log_status("Build of ".$testline." FAILED.\n");
tlog(1, "Build of ".$testline." FAILED.\n");
log_status("Entering: ".Cwd::abs_path("..")."\n");
chdir "..";
log_report(\%curr_test, $test_status);
# Print out pass/fail status for each test as it completes
$quietmode = $options{'quiet'}; # Backup quiet mode setting
$options{'quiet'} = 0;
if ($test_status == 0) {
log_status("Test ".$testline." PASSED.\n");
tlog(0, "Test ".$testline." PASSED.\n");
}
else {
log_status("Test ".$testline." FAILED.\n");
tlog(1, "Test ".$testline." FAILED.\n");
}
$options{'quiet'} = $quietmode; # Restore quiet mode setting
finish_logs();
# Link logs to global area and rename if running multiple tests
system("ln -sf ".$root_dir."/verify/".$curr_test{'id'}."/".$verify::logfile." ../".(($test_status > 0) ? "fail".$curr_test{'id'}.".log" : "pass".$curr_test{'id'}.".log" )) if (@tests > 1);
if ($options{'parallel'} > 0 && $pid == 0) {
# If we're in parallel mode and I'm a child process, I should exit, instead of continuing to loop.
finish_child($test_status);
}
else {
# If we're not in parallel mode, I should continue to loop.
next TEST_LOOP;
}
}
Here's the behavior that I'm seeing according to the log from a run I did:
<Parent> Waiting for all child processes to complete...
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Running user command: make --directory <trimmed> TARGET=build BUILD_DIR=<trimmed> RUN_DIR=<trimmed>
<Child> [PID 28657] User command finished with return code: 512
<Child> [PID 28657] Build step finished with return code 512
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Build of rx::basic(1) FAILED.
<Child> [PID 28657] Entering: <trimmed>
<Child> [PID 28657] Test rx::basic(1) FAILED.
<Child> [PID 28657] Closing log file.
<Child> [PID 28657] Closing error log file.
<Child> [PID 28657] Entering: <trimmed>
<Parent> Child process (PID 28657, test rx::basic(1)) exited with status 0.
I have code that uses Perl IPCs to run commands (in lieu of the system() call, for more flexibility that picks up the exit code properly, which you can see in the "User command" lines from the log file.
What could I be doing wrong, here? Why wouldn't I be able to pick up the exit status from $? in this case? The examples I found online all seem to indicate that this should work fine.
For reference, I'm running Perl v5.10.1. This Perl tool is also open sourced on GitHub if you feel you need to look through the rest of the code: https://github.com/benrichards86/Verify/blob/master/verify.pl
If $test_status is 512, are you calling POSIX::_exit(512)? That is incorrect.
A child process should call POSIX::_exit with an operand in the range 0 to 255, and the Perl parent process that reaps that child will get $? set to exit-status << 8.
POSIX::_exit(512) is equivalent to POSIX::_exit(512 % 256), or POSIX::_exit(0).
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