Date: Wed, 25 Mar 2009 12:59:20 -0400 From: John Baldwin <jhb@freebsd.org> To: Warner Losh <imp@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r189574 - head/sys/kern Message-ID: <200903251259.20921.jhb@freebsd.org> In-Reply-To: <200903091320.n29DKNT8027311@svn.freebsd.org> References: <200903091320.n29DKNT8027311@svn.freebsd.org>
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On Monday 09 March 2009 9:20:23 am Warner Losh wrote: > Author: imp > Date: Mon Mar 9 13:20:23 2009 > New Revision: 189574 > URL: http://svn.freebsd.org/changeset/base/189574 > > Log: > Fix a long-standing bug in newbus. It was introduced when subclassing > was introduced. If you have a bus, say cardbus, that is derived from > a base-bus (say PCI), then ordinarily all PCI drivers would attach to > cardbus devices. However, there had been one exception: kldload > wouldn't work. > > The problem is in devclass_add_driver. In this routine, all we did > was call to the pci device's BUS_DRIVER_ADDED routine. However, since > cardbus bus instances had a different devclass, none of them were > called. > > Modified: head/sys/kern/subr_bus.c > ============================================================================== > --- head/sys/kern/subr_bus.c Mon Mar 9 13:12:48 2009 (r189573) > +++ head/sys/kern/subr_bus.c Mon Mar 9 13:20:23 2009 (r189574) > @@ -82,6 +82,8 @@ struct devclass { > char *name; > device_t *devices; /* array of devices indexed by unit */ > int maxunit; /* size of devices array */ > + int flags; > +#define DC_HAS_CHILDREN 1 > > struct sysctl_ctx_list sysctl_ctx; > struct sysctl_oid *sysctl_tree; > @@ -813,6 +815,7 @@ devclass_find_internal(const char *class > if (parentname && dc && !dc->parent && > strcmp(classname, parentname) != 0) { > dc->parent = devclass_find_internal(parentname, NULL, FALSE); > + dc->parent->flags |= DC_HAS_CHILDREN; > } > > return (dc); So this is the cause of the recent reports of panics on boot. The problem is that when drivers are registered during boot they are loaded in a "random" order (depends on the order the objects are linked actually). The point, though, is that a subclass might register first. In that case, trying to set dc->parent will fail because the parent driver isn't registered yet, so dc->parent will be NULL when it tries to set DC_HAS_CHILDREN. Just not setting the flag if dc->parent is NULL will fix the panics, but I think you can have baseclasses that won't have DC_HAS_CHILDREN set. Perhaps the second devclass there should always create a devclass (i.e. last param is true)? Otherwise dc->parent could be NULL when it shouldn't be, either. I think that is probably the best solution. I've tested this and it worked. -- John Baldwin
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