#19022 [Fbk]: PHP Warning: Failed to write session data (files)

From: Date: Wed, 04 Sep 2002 13:41:38 +0000
Subject: #19022 [Fbk]: PHP Warning: Failed to write session data (files)
References: 1  Groups: php.bugs 
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 ID:               19022
 Updated by:       kalowsky@php.net
 Reported By:      phpbugs@mx4k.com
 Status:           Feedback
 Bug Type:         Session related
 Operating System: linux (rh7.3), apache 1.3.26
 PHP Version:      4.2.2
 New Comment:

Yes actually the PREAD functionality in the glibc has been found to be
buggy (this is actually in another bug report as well, I just forget
the number off hand).  It was fixed in the CVS for glibc, but that was
only as of July 2002.  

Regardless, try a snapshot for HEAD dated sometime after this point,
I've taken the PREAD out again.  Post back results.  


Previous Comments:
------------------------------------------------------------------------

[2002-09-04 06:35:48] phpbugs@mx4k.com

hi there,

as far as i can tell the problem only appears if the server runs on
middle to high load. (eg. >100httpd)

the problem machine is a p4-1,8ghz with 1gig ram (no smp) and we
couldnt yet reproduce the problem on any other server. the machine only
runs the httpd, postgres is running on a different machine. its using a
IDE hd (some special scsi or something)

i'm willing to apply some patches to get rid of the problem. i looked
into the problem myself but couldn't find any problem in PS(mod)->write
or the resulting write to the hd (which i guess is
PS_WRITE_FUNC(files)). I never coded on linux neither much of c (only
c++, c#, java) but maybe p/write does have a problem.

#ifdef HAVE_PWRITE  
        n = pwrite(data->fd, val, vallen, 0);
#else                   
        lseek(data->fd, 0, SEEK_SET);
        n = write(data->fd, val, vallen);
#endif

anyways, send me some patches via email and i'll try my best to find a
workarround.

greets,
thomas

------------------------------------------------------------------------

[2002-09-04 00:47:38] rasmus@php.net

Yup, the SMP means it likely has multiple processors.  "cat
/proc/cpuinfo" would tell you for sure.  A nasty bug was fixed recently
which only affected SMP machines and would cause exactly these
symptoms.  4.2.3 will have the fix.

------------------------------------------------------------------------

[2002-09-04 00:43:56] rossr@reactive.com

I'm not sure since we don't host the production site we are just the
developers. When I do a uname I get this:

Linux lsh129.siteprotect.com 2.4.18-pre7 #5 SMP Mon Feb 4 17:42:59 CST
2002 i686 unknown

I'm guessing that the SMP bit means that the server is using multiple
processors, but I'm not sure.

------------------------------------------------------------------------

[2002-09-04 00:29:58] rasmus@php.net

Your production server wouldn't happen to have multiple cpus?

------------------------------------------------------------------------

[2002-09-04 00:06:04] rossr@reactive.com

Hi there,

We didn't run into this problem until the site that we were working on
went live and we have been unable to replicate the problem on our dev
server in our office. 

So I'm guessing that the bug only appears on a loaded system.

Cheers, Ross

------------------------------------------------------------------------

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