mirror_zfs/lib
Matthew Macy 8056a75672
Disambiguate condvar API contract
On Illumos callers of cv_timedwait and cv_timedwait_hires
can't distinguish between whether or not the cv was signaled
or the call timed out. Illumos handles this (for some definition
of handles) by calling cv_signal in the return path if we were
signaled but the return value indicates instead that we timed
out. This would make sense if it were possible to query the the
cv for its net signal disposition. However, this isn't possible
and, in spite of the fact that there are places in the code that
clearly take a different and incompatible path if a timeout value
is indicated, this distinction appears to be rather subtle to most
developers. This problem is further compounded by the fact that on
Linux, calling cv_signal in the return path wouldn't even do the
right thing unless there are other waiters.

Since it is possible for the caller to independently determine how
much time is remaining but it is not possible to query if the cv
was in fact signaled, prioritizing signalling over timeout seems
like a cleaner solution. In addition, judging from usage patterns
within the code itself, it is also less error prone.

Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #10471
2020-06-18 10:17:50 -07:00
..
libavl OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libefi cppcheck: (error) Memory leak: vtoc 2019-12-18 17:25:04 -08:00
libicp ICP: Improve AES-GCM performance 2020-02-10 12:59:50 -08:00
libnvpair Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
libshare Fix static data to link with -fno-common 2020-02-06 09:25:29 -08:00
libspl Add convenience wrappers for common uio usage 2020-06-14 10:09:55 -07:00
libtpool OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libunicode OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libuutil Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
libzfs Fix typos 2020-06-09 21:24:09 -07:00
libzfs_core Add support for boot environment data to be stored in the label 2020-05-07 09:36:33 -07:00
libzpool Disambiguate condvar API contract 2020-06-18 10:17:50 -07:00
libzutil Remove refences to blacklist/whitelist 2020-06-16 11:41:45 -07:00
Makefile.am Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00