K 10
svn:author
V 3
mjg
K 8
svn:date
V 27
2018-03-04T21:38:30.984429Z
K 7
svn:log
V 666
locks: fix a corner case in r327399

If there were exactly rowner_retries/asx_retries (by default: 10) transitions
between read and write state and the waiters still did not get the lock, the
next owner -> reader transition would result in the code correctly falling
back to turnstile/sleepq where it would incorrectly think it was waiting
for a writer and decide to leave turnstile/sleepq to loop back. From this
point it would take ts/sq trips until the lock gets released.

The bug sometimes manifested itself in stalls during -j 128 package builds.

Refactor the code to fix the bug, while here remove some of the gratituous
differences between rw and sx locks.

END