Re: RELENG_5 panic [nic: _mtx_lock_sleep: recursed on non-recursivemutex nfsd_mtx]

Robert, 

The panic doesn't occur any longer since I upgraded world/kernel. Therefore
what you have written below would be pointless.

Are you suspecting that the bug is still there but not being triggered ?

I can downgrade world/kernel for testing if possible and needed ?

 - aW


	0n Mon, Oct 18, 2004 at 05:22:01AM -0400, Robert Watson wrote: 

	Hmm.  There was a bug in nfs_serv.c corrected on 2004/08/25 that corrected
	an incorrect lock pair, but I don't know of any related bugs corrrected
	since then.  If it's possible to get back to a point where this can be
	reproduced, configuring your kernel to run with KTR and to use KTR_LOCK
	would be quite helpful  You can find a bit of information on using KTR
	here:
	
	    http://www.watson.org/~robert/freebsd/netperf/ktr/
	
	Basically, once it panics, you can use the KTR-related commands in DDB to
	inspect the KTR buffer, and I believe also extract the KTR log from a core
	dump.  Using the set of KTR_COMPILE flags I have on that web page would be
	helpeful.  Basically, this generates a trace of locking, context switch,
	interrupt, callout, memory allocation, and system call events.  The
	problem likely occurred pretty immediately prior to the panic.
	
	If this is timing-related, it could be KTR disrupts the timing
	sufficiently to prevent it.  More likely, it went away because the work
	load on the NFS server changed, or the directory layout changed, or some
	other factor that caused the passage through the NFS code to change.
	
	Thanks!
	
	Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
	robert_at_fledge.watson.org      Principal Research Scientist, McAfee Research
	
	
	> 
	>  - aW
	> 
	> 
	> 
	> 	0n Sun, Oct 17, 2004 at 10:19:34AM -0400, Robert Watson wrote: 
	> 	
	> 	On Fri, 15 Oct 2004, Wilkinson, Alex wrote:
	> 	
	> 	> Hi all,
	> 	> 
	> 	> I currently get a panic with "nfs_server_enable=YES" in /etc/rc.conf.
	> 	> 
	> 	> OS: FreeBSD 5.3-BETA4 #2: Tue Sep 14 13:55:30 UTC 2004
	> 	> 
	> 	> Backtrace
	> 	> ---------
	> 	> 
	> 	> panic: _mtx_lock_sleep: recursed on non-recursive mutex nfsd_mtx _at_ /usr /src/sys/nfsserver/nfs_serv.c:1947
	> 	
	> 	Is the NFS server code compiled into your kernel, or is it getting loaded
	> 	as a module?  Do you have any other NFS-related entries in /etc/rc.conf?
	> 	Could you show the output of "show locks" and "show witness" with witness
	> 	compiled into the kernel?
	> 	
	> 	Thanks!
	> 	
	> 	Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
	> 	robert_at_fledge.watson.org      Principal Research Scientist, McAfee Research
	> 	
	> 	
	> 	> cpuid = 0
	> 	> KDB: enter: panic
	> 	> [thread 100074]
	> 	> Stopped at      kdb_enter+0x32: leave
	> 	> db> tr
	> 	> kdb_enter(c068ba66,0,c068aed8,dd2ed90c,c1b6b340) at kdb_enter+0x32
	> 	> panic(c068aed8,c069885f,c0698617,79b,c0698617) at panic+0x1b0
	> 	> _mtx_lock_sleep(c071c940,c1b6b340,0,c0698617,79b) at _mtx_lock_sleep+0x16e
	> 	> _mtx_lock_flags(c071c940,0,c0698617,79b,0) at _mtx_lock_flags+0xb0
	> 	> nfsrv_create(c1eb6800,c1b98800,c1b6b340,dd2edc8c,0) at nfsrv_create+0x8c4
	> 	> nfssvc(c1b6b340,dd2edd14,8,0,2) at nfssvc+0x6ea
	> 	> syscall(2f,2f,2f,0,0) at syscall+0x13b
	> 	> Xint0x80_syscall() at Xint0x80_syscall+0x1f
	> 	> --- syscall (155, FreeBSD ELF32, nfssvc), eip = 0x280c60bf, esp = 0xbfbfeb1c, eb p = 0xbfbfeb38 ---
	> 	> 
	> 	> 
	> 	>  - aW
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