wdc logs fixes from costa@:

1) wdc_get_log is at splbio() to prevent interrupt handlers from
updating the log
2) work hard to ensure that wdc_tail and wdc_head are between 0 and
wdc_log_cap, even if wdc_log or wdc_get_log is run concurrently against
itself. With this patch, running concurrent wdc_log's may corrupt the
log, but it should not cause any panics.
3) Make sure the buffer always starts on a record boundary. Otherwise
said, wdc_tail should always be on a record boundary.

0 files changed, 0 insertions, 0 deletions