CVS commit: [thorpej-futex2] src/sys/kern

["Jason R Thorpe" <thorpej%netbsd.org@localhost>]

Module Name:    src
Committed By:   thorpej
Date:           Thu Aug  5 23:23:50 UTC 2021

Modified Files:
        src/sys/kern [thorpej-futex2]: sys_futex.c

Log Message:
At the end of futex_wait(), when sleepq_block() returns 0, we would like
to assert that l->l_futex == NULL, because all of the code paths that awaken
a blocked thread in sys_futex.c itself clear l->l_futex.  Unfortunately,
there are certain received-a-signal situations (e.g. SIGKILL) where
sleepq_block() will not return an error after being awakened by the signal,
rendering this assertion too strong.

So, rather than going down the rabbit hole of reasoning out and altering
long-standing behavior of the signals code, just don't assert there and
treat a zero-return from sleepq_block() as an aborted futex wait if
l->l_futex != NULL.

(Thanks chs@ for helping chase this one down.)


To generate a diff of this commit:
cvs rdiff -u -r1.12.4.1 -r1.12.4.2 src/sys/kern/sys_futex.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.