Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753377Ab0HGMZR (ORCPT ); Sat, 7 Aug 2010 08:25:17 -0400 Received: from lo.gmane.org ([80.91.229.12]:35271 "EHLO lo.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752996Ab0HGMZN (ORCPT ); Sat, 7 Aug 2010 08:25:13 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Alexander Clouter Subject: Re: [PATCH]exit.c: support larger exit code Date: Sat, 7 Aug 2010 11:41:33 +0100 Message-ID: References: <14414B36FFA0F1418CB707361EAA199A0194F7D2@CNBEEXC006.nsn-intra.net> <20100806124456.GA9107@redhat.com> X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: chipmunk.wormnet.eu User-Agent: tin/1.9.3-20080506 ("Dalintober") (UNIX) (Linux/2.6.26-2-sparc64-smp (sparc64)) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3132 Lines: 75 Oleg Nesterov wrote: >> >> Nowadays userspace application use systemcall exit/exit_group only >> support one byte exit code. >> In some cases this exit code range is too small for some "big >> application"(like telecom software, 255 is not enough). >> >> So we can give some "big application" a chance to get larger exit code >> from child process. >> For other application don't want use larger exit code, they can use >> marco WEXITSTATUS to get lower one byte exit code. >> >> #define WEXITSTATUS(status) __WEXITSTATUS (__WAIT_INT (status)) >> --- stdlib.h >> #define __WEXITSTATUS(status) (((status) & 0xff00) >> 8) >> --- usrbits/waitstatus.h >> >> >> diff --git a/kernel/exit.c b/kernel/exit.c >> index ceffc67..8b13676 100644 >> --- a/kernel/exit.c >> +++ b/kernel/exit.c >> @@ -1045,7 +1045,7 @@ EXPORT_SYMBOL(complete_and_exit); >> >> SYSCALL_DEFINE1(exit, int, error_code) >> { >> - do_exit((error_code&0xff)<<8); >> + do_exit(error_code << 8); >> } >> >> /* >> @@ -1086,7 +1086,7 @@ do_group_exit(int exit_code) >> */ >> SYSCALL_DEFINE1(exit_group, int, error_code) >> { >> - do_group_exit((error_code & 0xff) << 8); >> + do_group_exit(error_code << 8); >> /* NOTREACHED */ >> return 0; >> } > > Hmm. Looking at this patch, I am wondering what was the reason for the > current one-byte limitation. > The one byte limitation I think is all that is needed to give an impression and *hint* of what went wrong, it was not ever meant to cover every possible error that the child process could report. Even "small programs" could generate $BIGNUM error codes it could be argued. Looking at the list for reserved exitcodes[1] everything covers operational use and then if you look to /usr/include/sysexits.h for an idea of the 'spirit' behind exitcodes, it is pretty clear it is all rather 'generic' and vague to the precise reason, but it categorises the type of error to maybe something the parent could gracefully handle. It is not a freetext communications channel :) If you have $BIGNUM outcomes of errors, you probably should not be using the exitcode path to communicate this information back up, although I would agree it looks like very natural solution. I would be more inclined to pass up to the parent this information via a pipe (whether that is via stdout, stderr or even a filesystem located pipe). No doubt if you are trying to return $BIGNUM error codes, you probably want to look more to an approach based on the one covered in RFC3463; there if you return a sysexits.h type code then the child's STDOUT is consulted for the extended error code reason...I think this approach is *very* nice. Cheers [1] http://tldp.org/LDP/abs/html/exitcodes.html#EXITCODESREF [2] http://tools.ietf.org/html/rfc3463 -- Alexander Clouter .sigmonster says: If in doubt, mumble. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/