Re: [sysctl] New sysctl LoR today

On Wednesday 11 February 2009 1:09:28 am Sean Bruno wrote:
> On Tue, 2009-02-10 at 17:23 -0800, Sean Bruno wrote:
> > I'm working on some items in the firewire stack and after a update, I
> > was greeted with a new LoR against the SYSCTL lock.  I noted that some
> > things were changing in that space.
> > 
> > Did I miss an interface change that I need to pickup in the firewire
> > stack?
> > 
> > Sean
> > 
> > lock order reversal: (sleepable after non-sleepable)
> >  1st 0xc471bbec sbp (sbp) _at_ dev/firewire/sbp.c:2253
> >  2nd 0xc0d3aea4 sysctl lock (sysctl lock) _at_ kern/kern_sysctl.c:250
> > KDB: stack backtrace:
> > _sx_xlock(c0d3aea4,0,c0be5d46,fa,c471a000,...) at _sx_xlock+0x85
> > sysctl_ctx_free(c471a2c0,c0b8f786,c0d0696c,0,c469fa0c,...) at
> > sysctl_ctx_free+0x30
> > dacleanup(c4c54700,c0b900bb,c480e000,c42aa410,246,...) at dacleanup+0x35
> > camperiphfree(c4c54700,c4c54700,c42aa694,c047763d,c4c54700,...) at

No, this is due to CAM calling sysctl_ctx_free() with a lock held.  You can 
try this change:

--- //depot/user/jhb/lock/cam/scsi/scsi_cd.c
+++ /home/jhb/work/p4/lock/cam/scsi/scsi_cd.c
_at__at_ -401,11 +401,6 _at__at_
 
 	xpt_print(periph->path, "removing device entry\n");
 
-	if ((softc->flags & CD_FLAG_SCTX_INIT) != 0
-	    && sysctl_ctx_free(&softc->sysctl_ctx) != 0) {
-		xpt_print(periph->path, "can't remove sysctl context\n");
-	}
-
 	/*
 	 * In the queued, non-active case, the device in question
 	 * has already been removed from the changer run queue.  Since this
_at__at_ -474,9 +469,14 _at__at_
 		free(softc->changer, M_DEVBUF);
 	}
 	cam_periph_unlock(periph);
+	if ((softc->flags & CD_FLAG_SCTX_INIT) != 0
+	    && sysctl_ctx_free(&softc->sysctl_ctx) != 0) {
+		xpt_print(periph->path, "can't remove sysctl context\n");
+	}
+
 	disk_destroy(softc->disk);
+	free(softc, M_DEVBUF);
 	cam_periph_lock(periph);
-	free(softc, M_DEVBUF);
 }
 
 static void
--- //depot/user/jhb/lock/cam/scsi/scsi_da.c
+++ /home/jhb/work/p4/lock/cam/scsi/scsi_da.c
_at__at_ -995,6 +995,8 _at__at_
 	softc = (struct da_softc *)periph->softc;
 
 	xpt_print(periph->path, "removing device entry\n");
+	cam_periph_unlock(periph);
+
 	/*
 	 * If we can't free the sysctl tree, oh well...
 	 */
_at__at_ -1003,11 +1005,10 _at__at_
 		xpt_print(periph->path, "can't remove sysctl context\n");
 	}
 
-	cam_periph_unlock(periph);
 	disk_destroy(softc->disk);
 	callout_drain(&softc->sendordered_c);
+	free(softc, M_DEVBUF);
 	cam_periph_lock(periph);
-	free(softc, M_DEVBUF);
 }
 
 static void


-- 
John Baldwin