Question

I have a seemingly simple problem. I need to execute a series of system commands (using backquotes) in parallel.

The code below has been stripped of anything meaningful besides demonstrating my problem:

#!/usr/bin/perl -w 
use strict; 
use threads; 
use POSIX; 
my @threads = (); 
sub timeout { 
  print "TIMEOUT
"; 
  foreach my $thread (@threads) { 
    $thread->kill("ALRM") if $thread->is_running(); 
  } 
} 

POSIX::sigaction(SIGALRM, POSIX::SigAction->new(&timeout)); 
alarm(2); 
sub threadsub { 
  sub handletimeout { 
    print "KILL
"; 
    threads->exit(1); 
  } 
  POSIX::sigaction(SIGALRM, POSIX::SigAction->new(&handletimeout)); 
  # while(1) { sleep(1); } 
  return `sleep 10`; 
} 

for(my $i=0; $i < 10; $i++) { 
  push(@threads, thread->create(&threadsub)); 
} 

foreach my $thread (@threads) { 
  my $res = $thread->join(); 
}

Now, the problem is the ALRM signal sent to the threads are never caught when the thread is blocked in the system call. If you uncomment the while loop the signal are caught as intended. How do I make this work so I m able to timeout my threads even if they re stuck in the system command?

感谢

Kasper

Answer 1

http://strong>man threads

   Unsafe signals
       Since Perl 5.8.0, signals have been made safer in Perl by postponing their handling until the interpreter is in a safe state.  See "Safe
       Signals" in perl58delta and "Deferred Signals (Safe Signals)" in perlipc for more details.

       Safe signals is the default behavior, and the old, immediate, unsafe signalling behavior is only in effect in the following situations:

       ?   Perl has been built with "PERL_OLD_SIGNALS" (see "perl -V").

       ?   The environment variable "PERL_SIGNALS" is set to "unsafe" (see "PERL_SIGNALS" in perlrun).

       ?   The module Perl::Unsafe::Signals is used.

       If unsafe signals is in effect, then signal handling is not thread-safe, and the "->kill()" signalling method cannot be used.

这种内分效应表明,信号将推迟到无安全状态。如果我们转向不安全的签字方案,用的电文终止。 Cannot sign threads without safety signs.pl. 请检查un-safe sign在您的系统中的工作。虽然它的工作是un-safe。建议移徙到进程。下面的法典应当给你预期的结果。

use strict;
use POSIX;

my $pid=fork();

sub timeout {
  print "TIMEOUT
";
  kill SIGALRM,$pid;
}

if( $pid ) { ## parent
    alarm(2);
    POSIX::sigaction(SIGALRM, POSIX::SigAction->new(&timeout));
    waitpid $pid,0;
} else { ## child
    sub handletimeout {
        print "SIGALRM child
";
        exit(1);
    }
    POSIX::sigaction(SIGALRM, POSIX::SigAction->new(&handletimeout));
    `sleep 10`;
    print "child normal exit";
}

友情链接