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| author | Rusty Russell <rusty@rustcorp.com.au> | 2008-04-07 14:30:28 +1000 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-07 13:14:22 -0700 |
| commit | 2557a933b795c1988c721ebb871cd735128bb9cb (patch) | |
| tree | 96581bd5acac44bbe0399aa445197509d9ae60ff /include | |
| parent | 4cac04dd63fa3b202ee313ed1afbbd135ab887ee (diff) | |
| download | blackbird-obmc-linux-2557a933b795c1988c721ebb871cd735128bb9cb.tar.gz blackbird-obmc-linux-2557a933b795c1988c721ebb871cd735128bb9cb.zip | |
virtio: remove overzealous BUG_ON.
The 'disable_cb' callback is designed as an optimization to tell the host
we don't need callbacks now. As it is not reliable, the debug check is
overzealous: it can happen on two CPUs at the same time. Document this.
Even if it were reliable, the virtio_net driver doesn't disable
callbacks on transmit so the START_USE/END_USE debugging reentrance
protection can be easily tripped even on UP.
Thanks to Balaji Rao for the bug report and testing.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
CC: Balaji Rao <balajirrao@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/virtio.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 12c18ac1b973..e7d10845b3c1 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -41,6 +41,8 @@ struct virtqueue * Returns NULL or the "data" token handed to add_buf. * @disable_cb: disable callbacks * vq: the struct virtqueue we're talking about. + * Note that this is not necessarily synchronous, hence unreliable and only + * useful as an optimization. * @enable_cb: restart callbacks after disable_cb. * vq: the struct virtqueue we're talking about. * This re-enables callbacks; it returns "false" if there are pending @@ -48,7 +50,8 @@ struct virtqueue * checking for more work, and enabling callbacks. * * Locking rules are straightforward: the driver is responsible for - * locking. No two operations may be invoked simultaneously. + * locking. No two operations may be invoked simultaneously, with the exception + * of @disable_cb. * * All operations can be called in any context. */ |
