[uClibc 0001551]: Poll with zero or negative timeout

[bugs at busybox.net]

The following issue has been RESOLVED. 
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http://busybox.net/bugs/view.php?id=1551 
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Reported By:                jcdr
Assigned To:                uClibc
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Project:                    uClibc
Issue ID:                   1551
Category:                   Standards Compliance
Reproducibility:            always
Severity:                   block
Priority:                   normal
Status:                     resolved
Resolution:                 fixed
Fixed in Version:           
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Date Submitted:             10-23-2007 00:18 PDT
Last Modified:              10-23-2007 11:07 PDT
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Summary:                    Poll with zero or negative timeout
Description: 
Hello,

I tried to use the bug tracking system, but the "Report Issue" page never
go after the "Select Project" form. So I post this patch here.

The attached patch solve an issue I faced while using the libdbus-glib
waiting for a D-Bus message or the end of a glib timer at the same time.
This specific case of use generate a poll call with a zero timeout. On
platformes with the glibc a zero timeout poll return immetiately even if
there is no file descriptor event. But on platformes with uClibc a zero
timeout poll block until a file descriptor event occurs.

I found that the file libc/sysdeps/linux/common/poll.c only take care of 
positive timeout and pass a null pointer in case of a zero or negative
timeout, making the zero and negative the same case: blocking.

The patch alway pass a valid structure for the timeout of poll and assign
acceptable timeout values for the zero and negative case by avoiding the
math needed for positive timeout value.

This has been tested on a Blackfin BF533 processor.

Have a good day,
-- 
Jean-Christian de Rivaz

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---------------------------------------------------------------------- 
 jcdr - 10-23-07 04:07  
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Joakim Tjernlund a écrit :
> And why not pass NULL as it was before?

The man 2 ppoll say:

"If timeout is specified as NULL, then ppoll() can block indefinitely."

So you are right, it's possible to passe a null pointer to do the same as
negative value.

The poll-zero-timeout.txt patch improve this. 

---------------------------------------------------------------------- 
 jocke - 10-23-07 11:07  
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fixed in uClibc trunk 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
10-23-07 00:18  jcdr           New Issue                                    
10-23-07 00:18  jcdr           Status                   new => assigned     
10-23-07 00:18  jcdr           Assigned To               => uClibc          
10-23-07 00:18  jcdr           File Added: poll-zero-or-negative-timeout.txt    
               
10-23-07 00:49  jcdr           Issue Monitored: jcdr                        
10-23-07 04:06  jcdr           File Added: poll-zero-timeout.txt                
   
10-23-07 04:07  jcdr           Note Added: 0002858                          
10-23-07 11:07  jocke          Status                   assigned => resolved
10-23-07 11:07  jocke          Resolution               open => fixed       
10-23-07 11:07  jocke          Note Added: 0002859                          
======================================================================