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Bug 232236

Summary: Exit notifications missing when tracing multi-threaded processes
Product: [Fedora] Fedora Reporter: Magnus Vesterlund <magnus_vesterlund>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED CURRENTRELEASE QA Contact: Brian Brock <bbrock>
Severity: medium Docs Contact:
Priority: medium    
Version: 6CC: roland
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: 2.6.20-1.2933.fc6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2007-04-02 14:00:00 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On:    
Bug Blocks: 232369    
Attachments:
Description Flags
Test case
none
test case contained in one source file
none
fix patch none

Description Magnus Vesterlund 2007-03-14 15:08:30 UTC
Description of problem:
When tracing multiple threads in a process using ptrace the Fedora Core kernel
only delivers an exit notification through wait for the initial thread. Vanilla
Linux kernels deliver an exit notification for each traced thread.

Version-Release number of selected component (if applicable):
2.6.19-1.2911.6.5.fc6

How reproducible:
Every time.

Steps to Reproduce:
1. Untar the attached test.
2. cd exit-test
3. make
4. ./monitor

Actual results:
Prints only one exit notification.

Expected results:
Should print two exit notifications.

Additional info:

For a less synthetic testcase, strace is also affected by this. Try compiling
this program with "gcc -fopenmp -o foo foo.c":

int main(int argc, char **argv) {
    int i;
#pragma omp parallel for
    for (i = 0; i < 1; i++)
        ;

    return 0;
}

Then trace it with "strace -f ./foo". Strace reports multiple detaches for the
same thread or bogus SIGSEGVs:

...
[pid  4586] futex(0x886b048, FUTEX_WAKE, 1) = 1
[pid  4585] <... futex resumed> )       = 0
[pid  4585] futex(0x886b048, FUTEX_WAKE, 1) = 0
[pid  4585] exit_group(0)               = ?
Process 4585 detached
Process 4586 detached
Process 4585 detached

...
[pid  4589] futex(0x19d830, FUTEX_WAIT, 0, NULL <unfinished ...>
[pid  4588] <... futex resumed> )       = 0
[pid  4588] exit_group(0)               = ?
[pid  4589] <... futex resumed> )       = 9
[pid  4589] --- SIGSEGV (Segmentation fault) @ 0 (0) ---

Comment 1 Magnus Vesterlund 2007-03-14 15:08:30 UTC
Created attachment 150042 [details]
Test case

Comment 2 Chuck Ebbert 2007-03-14 15:13:47 UTC
Please test 2.6.20-1.2925.fc6

It's in Fedora testing now and should be released today.

Comment 3 Roland McGrath 2007-03-14 18:53:35 UTC
Looks like this is still a problem.

Comment 4 Roland McGrath 2007-03-15 00:14:54 UTC
Created attachment 150103 [details]
test case contained in one source file

This is the version of the test case I'm using.

Comment 5 Roland McGrath 2007-03-15 00:56:12 UTC
Created attachment 150106 [details]
fix patch

I've fixed the bug and the attached patch is now part of the "upstream" utrace
patches.

Comment 6 Roland McGrath 2007-03-15 01:01:09 UTC
I've committed the new utrace patch to the rawhide kernel cvs.
The attached patch can be folded into the utrace patch for fc6.

Comment 7 Chuck Ebbert 2007-03-30 22:08:42 UTC
Is this bug fixed? Kernel 2933 is out with this fix and kernel 2937
or better (from http://people.redhat.com/cebbert) has more fixes.

Comment 8 Magnus Vesterlund 2007-04-01 07:19:28 UTC
Yes, the bug is fixed in both 2933 and 2937.