re: kern/49709: radeondrmkms panic if "/dev/" is on NFS root

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR kern/49709; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
    netbsd-bugs%netbsd.org@localhost
Subject: re: kern/49709: radeondrmkms panic if "/dev/" is on NFS root
Date: Mon, 02 Mar 2015 16:29:31 +1100

 > >Synopsis:       radeondrmkms panic if "/dev/" is on NFS root
 
 actually, it's a timing issue, not NFS root related.
 
 the problem is that /sbin/init is allowed to run as soon as mountroot
 completes, but before the paused configuration threads complete their
 task and in this case, the radeondrmkms driver has not gotten to
 attaching a wsdisplay0 and taking over the console.
 
 fortunately, we have working fixes for this, and are just trying to
 figure out which is the best.  one that i've tested that work is
 below.
 
 
 .mrg.
 
 
 Index: sys/device.h
 ===================================================================
 RCS file: /cvsroot/src/sys/sys/device.h,v
 retrieving revision 1.146
 diff -p -u -r1.146 device.h
 --- sys/device.h	22 Nov 2014 11:04:57 -0000	1.146
 +++ sys/device.h	1 Mar 2015 13:02:53 -0000
 @@ -479,6 +479,7 @@ void	config_create_mountrootthreads(void
  
  int	config_finalize_register(device_t, int (*)(device_t));
  void	config_finalize(void);
 +void	config_finalize_mountroot(void);
  
  void	config_twiddle_init(void);
  void	config_twiddle_fn(void *);
 Index: kern/init_main.c
 ===================================================================
 RCS file: /cvsroot/src/sys/kern/init_main.c,v
 retrieving revision 1.461
 diff -p -u -r1.461 init_main.c
 --- kern/init_main.c	27 Nov 2014 14:38:09 -0000	1.461
 +++ kern/init_main.c	1 Mar 2015 13:02:53 -0000
 @@ -712,6 +712,9 @@ main(void)
  	    uvm_aiodone_worker, NULL, PRI_VM, IPL_NONE, WQ_MPSAFE))
  		panic("fork aiodoned");
  
 +	/* Wait for final configure threads to complete. */
 +	config_finalize_mountroot();
 +
  	/*
  	 * Okay, now we can let init(8) exec!  It's off to userland!
  	 */
 Index: kern/subr_autoconf.c
 ===================================================================
 RCS file: /cvsroot/src/sys/kern/subr_autoconf.c,v
 retrieving revision 1.233
 diff -p -u -r1.233 subr_autoconf.c
 --- kern/subr_autoconf.c	6 Nov 2014 08:46:04 -0000	1.233
 +++ kern/subr_autoconf.c	1 Mar 2015 13:02:53 -0000
 @@ -202,6 +202,7 @@ int interrupt_config_threads = 8;
  struct deferred_config_head mountroot_config_queue =
  	TAILQ_HEAD_INITIALIZER(mountroot_config_queue);
  int mountroot_config_threads = 2;
 +lwp_t **mountroot_config_lwpids;
  static bool root_is_mounted = false;
  
  static void config_process_deferred(struct deferred_config_head *, device_t);
 @@ -481,9 +482,32 @@ config_create_mountrootthreads(void)
  	if (!root_is_mounted)
  		root_is_mounted = true;
  
 +	mountroot_config_lwpids = kmem_alloc(sizeof(mountroot_config_lwpids) *
 +					     mountroot_config_threads,
 +					     KM_NOSLEEP);
 +	KASSERT(mountroot_config_lwpids);
  	for (i = 0; i < mountroot_config_threads; i++) {
 -		(void)kthread_create(PRI_NONE, 0, NULL,
 -		    config_mountroot_thread, NULL, NULL, "configroot");
 +		mountroot_config_lwpids[i] = 0;
 +		(void)kthread_create(PRI_NONE, KTHREAD_MUSTJOIN, NULL,
 +				     config_mountroot_thread, NULL,
 +				     &mountroot_config_lwpids[i],
 +				     "configroot");
 +	}
 +}
 +
 +void
 +config_finalize_mountroot(void)
 +{
 +	int i, error;
 +
 +	for (i = 0; i < mountroot_config_threads; i++) {
 +		if (mountroot_config_lwpids[i] == 0)
 +			continue;
 +
 +		error = kthread_join(mountroot_config_lwpids[i]);
 +		if (error)
 +			printf("%s: thread %x joined with error %d\n",
 +			       __func__, i, error);
  	}
  }