Subject: NFS mounting of root filesystem on Assabet

From: Jeff Sutherland <[email-masked]>
Date: Tue, 20 Jun 2000 10:17:29 -0400

Has anyone successfully NFS mounted a root filesystem for their Assabet at
boot time?  I'm running down what appears to be a spinlock issue in
2.4.0-test1-ac19-rmk1-np1 in function get_write_access() in fs/openi.c.  The
simple (non-irq) spinlocks spin_lock() and spin_unlock() are being used
here, but the file /dev/console is being redirected to /dev/ttyS0 currently.
Execution seems to stall following atomic_inc() near the end of fs/openi.c
get_write_acces() in what appears to be a spin deadlock.  LED D8 continues
to blink for about 10 seconds (D9 is on solid) after reaching this point,
after which D8 stops and the kernel croaks.  Do we need to possibly use the
safer (but slower) write_lock_irqsave() and write_unlock_irqsave() here
instead?  Some insight please...

//Jeff

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From: Russell King - ARM Linux Admin <[email-masked]>
Date: Tue, 20 Jun 2000 20:40:00 +0100 (BST)

Jeff Sutherland writes:
> 2.4.0-test1-ac19-rmk1-np1 in function get_write_access() in fs/openi.c.

spinlocks don't do anything on ARM, except the irq versions which enable/disable
interrupts.
   _____
  |_____| ------------------------------------------------- ---+---+-
  |   |        Russell King       [email-masked]      --- ---
  | | | |            http://www.arm.linux.org.uk/            /  /  |
  | +-+-+                                                     --- -+-
  /   |               THE developer of ARM Linux              |+| /|\
 /  | | |                                                     ---  |
    +-+-+ -------------------------------------------------  /\\\  |

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From: Russell King - ARM Linux Admin <[email-masked]>
Date: Tue, 20 Jun 2000 20:43:17 +0100 (BST)

Jeff Sutherland writes:
> boot time?

Oh, NFS root filesystems do work on these kernels - my EBSA110 is running
root-NFS'd ac19 at the moment (will be running ac22 later tonight).
   _____
  |_____| ------------------------------------------------- ---+---+-
  |   |        Russell King       [email-masked]      --- ---
  | | | |            http://www.arm.linux.org.uk/            /  /  |
  | +-+-+                                                     --- -+-
  /   |               THE developer of ARM Linux              |+| /|\
 /  | | |                                                     ---  |
    +-+-+ -------------------------------------------------  /\\\  |

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From: Nicolas Pitre <[email-masked]>
Date: Tue, 20 Jun 2000 16:33:48 -0400 (EDT)

> root-NFS'd ac19 at the moment (will be running ac22 later tonight).

The problem with Assabet is the ethernet device is PCMCIA.  So the initrd
must contain the /linuxrc + PCMCIA tools to make a network card actually
apear before the real root FS i.e. NFS is mounted.  Thus the real problem
is executing /linuxrc, not NFS root.

Nicolas