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[Bug threads/11593] New: mi-nsmoribund.exp: unexpected stop
- From: "jan dot kratochvil at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: gdb-prs at sourceware dot org
- Date: 12 May 2010 13:12:35 -0000
- Subject: [Bug threads/11593] New: mi-nsmoribund.exp: unexpected stop
- Reply-to: sourceware-bugzilla at sourceware dot org
at least on Fedora kernels (tested kernel-2.6.32.12-116.fc12.x86_64) ptrace
implemented on top of utrace gdb.mi/mi-nsmoribund.exp randomly FAILs:
FAIL: gdb.mi/mi-nsmoribund.exp: unexpected stop
It is due to moribund breakpoint location being retired too early.
Unaware if it happens with legacy ptrace implementation, it probably does not.
utrace has been optimized for the best parallelization for maximum performance
on multicore systems while still maintaining full ptrace backward
compatibility.
In the attached new debug messages instrumentated debug dump one can see
LWP 12856 has been still running the time "-break-delete" has been executed,
then (too) many stop-and-continue operations happened for other LWPs and only
then LWP 12856 finally reported SIGTRAP having already its moribund breakpoint
location retired.
Any increased value of this expression cannot help to fix the bug:
old_loc->events_till_retirement = 3 * (thread_count () + 1);
I believe to safely retire moribunds each existing thread must get into
(a) !is_executing() state and
(b) all its events must get processed.
The (b) requirement may cause moribunds to be never retired during some
debugging situations. Also unaware how to find the (b) point now,
stop_and_resume_callback is needlessly expensive.
--
Summary: mi-nsmoribund.exp: unexpected stop
Product: gdb
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: threads
AssignedTo: unassigned at sourceware dot org
ReportedBy: jan dot kratochvil at redhat dot com
CC: gdb-prs at sourceware dot org,pedro at codesourcery dot
com
GCC target triplet: x86_64-fedora12-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=11593
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