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Bug #71209 php-cgi script hangs when started from php-fpm via system(), passthru() etc.
Submitted: 2015-12-24 03:17 UTC Modified: 2016-07-15 10:12 UTC
From: lameventanas at gmail dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 5.6.16 / 7.0.1 OS: Linux
Private report: No CVE-ID: None
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 [2015-12-24 03:17 UTC] lameventanas at gmail dot com 
Description:
------------
My lighttpd server uses fastcgi to run php code.

The php code starts an external program that happens to be a standalone php script (shebang: #!/usr/bin/php-cgi).

The script hangs when started from a php-fpm process manager, but works fine when started from a php-cgi "process manager".

Just to clarify, the process that hangs is the php-cgi which is interpreting the standalone script.  If I replace this with a shellscript, everything works fine.

Test script:
---------------
test.php:
<?
header("Content-type: text/plain");
echo "Starting\n";
system("/var/www/htdocs/script.php");
echo "Finished\n";
?>

script.php:
#!/usr/bin/php-cgi -q
<?
echo "Hello world!\n";
?>


Expected result:
----------------
No hangs.

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 [2015-12-24 10:44 UTC] lameventanas at gmail dot com 
This didn't happen with 5.6.2, but I'm uncertain of which version introduced the change.

Note that /usr/bin/php-cgi is SAPI cgi-fcgi.
was compiled with --disable-cli and --enable-cgi.

If I use #!/usr/bin/php in script.php (CLI SAPI), it doesn't hang.
 [2015-12-25 06:24 UTC] lameventanas at gmail dot com
-PHP Version: 5.6.16 +PHP Version: 5.6.16 7/.0.1
 [2015-12-25 06:24 UTC] lameventanas at gmail dot com 
Disregard my previous comment, the same thing happens with 5.6.2, and even 7.0.1.
 [2016-01-05 02:10 UTC] lameventanas at gmail dot com
-PHP Version: 5.6.16 7/.0.1 +PHP Version: 5.6.16 / 7.0.1
 [2016-01-05 02:10 UTC] lameventanas at gmail dot com 
Fixed versions.
 [2016-03-17 09:12 UTC] lameventanas at gmail dot com 
I found that php-cgi is stuck trying to call accept() on stdin:

...
22730 rt_sigaction(SIGPIPE, {SIG_IGN, [PIPE], SA_RESTART}, {SIG_IGN, [PIPE], SA_RESTART}, 8) = 0
22730 brk(0x882d000)                    = 0x882d000
22730 gettimeofday({1458204368, 785265}, NULL) = 0
22730 open("/tmp/.ZendSem.FT3dUS", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
22730 fchmod(3, 0666)                   = 0
22730 fcntl64(3, F_GETFD)               = 0
22730 fcntl64(3, F_SETFD, FD_CLOEXEC)   = 0
22730 unlink("/tmp/.ZendSem.FT3dUS")    = 0
22730 mmap2(NULL, 67108864, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS|0x40000, -1, 0) = -1 ENOMEM (Cannot allocate memory)
22730 mmap2(NULL, 67108864, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0) = 0xae200000
22730 fcntl64(3, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
22730 time(NULL)                        = 1458204368
22730 fcntl64(3, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
22730 fcntl64(3, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
22730 fcntl64(3, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
22730 brk(0x884e000)                    = 0x884e000
22730 accept(0, 

So I changed my test script to:

system("/var/www/htdocs/script.php < /dev/null");

and it doesn't hang anymore!
 [2016-07-15 10:12 UTC] dmitry@php.net
-Status: Open +Status: Not a bug
 [2016-07-15 10:12 UTC] dmitry@php.net 
You use php-cgi to run CLI script, but when you start it from FPM process, php-cgi thinks - it's a FastCGI server itself and waits for requests on STDIN.

Use php instead of php-cgi.
 
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