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[Bug kprobes/2637] skipped probes in FC6
- From: "prasanna at in dot ibm dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 5 May 2006 06:56:35 -0000
- Subject: [Bug kprobes/2637] skipped probes in FC6
- References: <20060502201312.2637.hunt@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From prasanna at in dot ibm dot com 2006-05-05 06:56 -------
The example given by Martin, accesses the data in user address space. Most
likely the data accessed from user address space may not be present in memory.
It is known that such accesses causes page_faults, where in the
fixup_exception() may not succeed most of the times, hence nmissed count goes up
(even with the current above patch).
Should we remove incrementing the nmissed count even if fixup_exception() fails?
Most of the system calls access user address space to copy the agruments and
they may experience the similar page_faults as above.
Is it acceptable, if the probe handler fails most of the time, while accessing
arguments from user address space. OR do we need to find some other way to
get the agruments of the syscalls?
Any thoughts?
Thanks
Prasanna
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2637
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