Bug 141896

Summary: false ECHILD result from wait* with zombie group leader
Product: [Fedora] Fedora Reporter: Roland McGrath <roland>
Component: kernelAssignee: Roland McGrath <roland>
Status: CLOSED NEXTRELEASE QA Contact: Brian Brock <bbrock>
Severity: low Docs Contact:
Priority: medium    
Version: rawhideCC: davej, drepper, mingo, wtogami
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OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2005-01-03 08:33:34 UTC Type: ---
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Description Flags
test case for wait bug
none
proposed fix none

Description Roland McGrath 2004-12-04 22:21:15 UTC 
Description of problem:

wait* syscall can sometimes return ECHILD though a multithreaded process child
exists and is in the process of exitting.

Version-Release number of selected component (if applicable):

2.6.9 or thereabouts.

How reproducible:
test program does 50 runs, usually happens in < 10 on 2-CPU machine

Steps to Reproduce:
1. gcc -g waitpidbug.c -lpthread -o waitpidbug
2. ./waitpidbug
3.
  
Actual results:
Will eventually say "Kill failed!", exit 1.

Expected results:
No such error from test program, exit 0.

Additional info:

Fix on the way.
Comment 1 Roland McGrath 2004-12-04 22:21:15 UTC 
Created attachment 107907 [details]
test case for wait bug
Comment 2 Roland McGrath 2004-12-04 22:23:14 UTC 
Created attachment 107908 [details]
proposed fix

I've just posted this fix upstream.
Comment 3 Ulrich Drepper 2004-12-13 10:38:49 UTC 
Seems to work nicely with 2.6.9-1.1032_FC4smp.  But I only tested the SMP kernel
on a UP HT machine.
Comment 4 Roland McGrath 2004-12-14 02:23:45 UTC 
Patch is in 2.6.10-rc3-mm1 tree upstream, not yet in Linus tree.
Comment 5 Roland McGrath 2004-12-24 23:59:36 UTC 
This went into Linus's kernel and should be in 2.6.10 when released.
Comment 6 Roland McGrath 2005-01-03 08:33:34 UTC 
2.6.10 has this fixed.