kern/90269: panic in pmc sampling mode

Eric Anholt anholt at
Sun Dec 11 21:10:04 PST 2005

>Number:         90269
>Category:       kern
>Synopsis:       panic in pmc sampling mode
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Dec 12 05:10:02 GMT 2005
>Originator:     Eric Anholt
>Release:        FreeBSD 7.0-CURRENT amd64
System: FreeBSD 7.0-CURRENT FreeBSD 7.0-CURRENT #22: Thu Dec 1 01:48:14 PST 2005 anholt at amd64

	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.
	Install liboil from ports
	Download and build libpcg from my website:
	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 :)



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