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* [Bug gdb/13426] New: Double-removals of JIT code info
@ 2011-11-21 23:42 sphink at gmail dot com
0 siblings, 0 replies; only message in thread
From: sphink at gmail dot com @ 2011-11-21 23:42 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13426
Bug #: 13426
Summary: Double-removals of JIT code info
Product: gdb
Version: unknown
Status: NEW
Severity: normal
Priority: P2
Component: gdb
AssignedTo: unassigned@sourceware.org
ReportedBy: sphink@gmail.com
Classification: Unclassified
Created attachment 6069
--> http://sourceware.org/bugzilla/attachment.cgi?id=6069
gdb debug output for double-unregistration
I am using the jit code registration API, and occasionally I see errors from
gdb that look like:
Unable to find JITed code entry at address: 0xffc730
The problem seems to be that it is doing a double-unregister: it unregisters
once successfully, then unregisters again and fails to find it.
I turned on debug_infrun and got output that suggests that the problem may be
that the inferior is getting a SIGPROF signal during the handling of the
__jit_debug_register_code() breakpoint, and somehow that triggers re-processing
the same unregistration event. (I am working on a SIGPROF-based profiler that
makes use of the JIT code registration information, so this would indeed happen
occasionally.)
gdb seems to recognize that the SIGPROF should be ignored:
infrun: random signal 27
infrun: signal arrived while stepping over breakpoint
but then it seems to see another SIGTRAP at the same stop_pc that it doesn't in
the absence of the SIGPROF. (So gdb sees SIGTRAP,SIGPROF,SIGTRAP without the
inferior advancing.)
I have modified the gdb source a bit to try to track this down, so the attached
output may have some minor differences from HEAD. The 'NUKE objf=0x695d410'
comes from jit_unregister_code(), which means it successfully removed an entry.
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2011-11-21 23:42 [Bug gdb/13426] New: Double-removals of JIT code info sphink at gmail dot com
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