kern/90269: panic in pmc sampling mode

[Eric Anholt]

>Number:         90269
>Category:       kern
>Synopsis:       panic in pmc sampling mode
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Dec 12 05:10:02 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Eric Anholt
>Release:        FreeBSD 7.0-CURRENT amd64
>Organization:
>Environment:
System: FreeBSD leguin.anholt.net 7.0-CURRENT FreeBSD 7.0-CURRENT #22: Thu Dec 1 01:48:14 PST 2005 anholt at leguin.anholt.net:/usr/obj/usr/src/current/sys/MYKERNEL amd64


	
>Description:
	Attempting to use pmc to profile a library I'm working on results in
	panics.  While I couldn't get a dump, here's the backtrace:

	kdb_enter() at kdb_enter+0x2f
	panic() at panic+0x249
	pmc_release_pmc_descriptor() at pmc_release_pmc_descriptor+0x2eb
	pmc_syscall_handler() at pmc_syscall_handler+0x41a
	syscall() at syscall+0x217
	Xfast_syscall() at Xfast_syscall+0xa8

	I didn't get the panic str, it looks like.  Started my minicom log too
	late.  I'll get that later by reproducing, but wanted to get the bug
	filed for now.
>How-To-Repeat:
	Install liboil from ports
	Download and build libpcg from my website:
		http://www.anholt.net/libpcg/release/libpcg-0.2.1.tar.bz2
	Try to run a shell script containing:
		pmcstat -S instructions -O samples.out ./tests/timing
		pmcstat -R samples.out -g
	Watch your serial console.  It'll run for a couple of seconds, but then
	die (perhaps around the time that the program should be ending).

	I suspect the actual list of steps is not so specific, but it's what I'm
	using (modulo that I'm using current libpcg sources that I'm working on
	making faster :)
>Fix:

	


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>Audit-Trail:
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