[Mono-bugs] [Bug 442316] New: Mono GC hangs in 100% CPU loop

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=442316


           Summary: Mono GC hangs in 100% CPU loop
           Product: Mono: Runtime
           Version: 1.9
          Platform: x86-64
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: GC
        AssignedTo: lupus at novell.com
        ReportedBy: zlynx at acm.org
         QAContact: mono-bugs at lists.ximian.com
          Found By: Community User


Description of Problem:
The Mono program Beagle shows this problem on my laptop.  At some point during
the execution of beagled-helper, it enters a 100% CPU loop and does not exit.

Investigation of the beagled-helper process with kill -QUIT and gdb show that
it is stuck in a tight loop on line 229 of pthread_support.c in the
return_freelists function.

The line is:
for (; (word)q >= HBLKSIZE; qptr = &(obj_link(q)), q = *qptr);

The disassembly of the loop is:
0x00000000004f8470 <return_freelists+32>:       mov    %rax,%rdx
0x00000000004f8473 <return_freelists+35>:       mov    (%rax),%rax
0x00000000004f8476 <return_freelists+38>:       cmp    $0xfff,%rax
0x00000000004f847c <return_freelists+44>:       ja     0x4f8470

The value of %rax (which is q I believe) is always 0x24636d8 because the value
of *qptr is also 0x24636d8.

Steps to reproduce the problem:
I am not entirely sure.  In my case, I just have to let beagle run indexing on
Evolution email until it happens.

Actual Results:
A tight loop, very high CPU temperature, lots of fan noise.

Expected Results:
Beagle indexing completion without fuss.

How often does this happen? 
Every time Beagle launches after user login, eventually after some period of
time.


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