branch.
This function is used to drain a callout via a callback instead of
blocking the caller until the drain is complete. Refer to the
callout_drain_async() manual page for a detailed description.
Limitation: If a lock is used with the callout, the callout can only
be drained asynchronously one time unless the callout_init_mtx()
function is called again. This limitation is not present in
projects/hps_head and will require more invasive changes to the
timeout code, which was not in the scope of this patch.
Differential Revision: https://reviews.freebsd.org/D3521
Reviewed by: wblock
MFC after: 1 month
FreeBSD developers need more time to review patches in the surrounding
areas like the TCP stack which are using MPSAFE callouts to restore
distribution of callouts on multiple CPUs.
Bump the __FreeBSD_version instead of reverting it.
Suggested by: kmacy, adrian, glebius and kib
Differential Revision: https://reviews.freebsd.org/D1438
- Close a migration race where callout_reset() failed to set the
CALLOUT_ACTIVE flag.
- Callout callback functions are now allowed to be protected by
spinlocks.
- Switching the callout CPU number cannot always be done on a
per-callout basis. See the updated timeout(9) manual page for more
information.
- The timeout(9) manual page has been updated to reflect how all the
functions inside the callout API are working. The manual page has
been made function oriented to make it easier to deduce how each of
the functions making up the callout API are working without having
to first read the whole manual page. Group all functions into a
handful of sections which should give a quick top-level overview
when the different functions should be used.
- The CALLOUT_SHAREDLOCK flag and its functionality has been removed
to reduce the complexity in the callout code and to avoid problems
about atomically stopping callouts via callout_stop(). If someone
needs it, it can be re-added. From my quick grep there are no
CALLOUT_SHAREDLOCK clients in the kernel.
- A new callout API function named "callout_drain_async()" has been
added. See the updated timeout(9) manual page for a complete
description.
- Update the callout clients in the "kern/" folder to use the callout
API properly, like cv_timedwait(). Previously there was some custom
sleepqueue code in the callout subsystem, which has been removed,
because we now allow callouts to be protected by spinlocks. This
allows us to tear down the callout like done with regular mutexes,
and a "td_slpmutex" has been added to "struct thread" to atomically
teardown the "td_slpcallout". Further the "TDF_TIMOFAIL" and
"SWT_SLEEPQTIMO" states can now be completely removed. Currently
they are marked as available and will be cleaned up in a follow up
commit.
- Bump the __FreeBSD_version to indicate kernel modules need
recompilation.
- There has been several reports that this patch "seems to squash a
serious bug leading to a callout timeout and panic".
Kernel build testing: all architectures were built
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D1438
Sponsored by: Mellanox Technologies
Reviewed by: jhb, adrian, sbruno and emaste
of timeout(9) to the end and mark it prominently as deprecated. Document
somewhat how times are specified for the 'sbt' variants. Better explain
how using callout_init_*() to associate a lock with a callout resolves
common races.
Differential Revision: https://reviews.freebsd.org/D847
Reviewed by: wblock, bjk
MFC after: 1 week
with rmlocks. This works only with non-sleepable rm because handlers run
in SWI context. While here, document the new KPI in the timeout(9)
manpage.
Requested by: adrian, scottl
Reviewed by: mav, remko(manpage)
callout is first initialised, using a new function callout_init_mtx().
The callout system will acquire this mutex before calling the callout
function and release it on return.
In addition, the callout system uses the mutex to avoid most of the
complications and race conditions inherent in asynchronous timer
facilities, so mutex-protected callouts have much simpler semantics.
As long as the mutex is held when invoking callout_stop() or
callout_reset(), then these functions will guarantee that the callout
will be stopped, even if softclock() had already begun to process
the callout.
Existing Giant-locked callouts will automatically pick up the new
race-free semantics. This should close a number of race conditions
in the USB code and probably other areas of the kernel too.
There should be no change in behaviour for "MP-safe" callouts; these
still need to use the techniques mentioned in timeout(9) to avoid
race conditions.
when using the callout subsystem. Show how the callout_pending(),
callout_active() and callout_deactivate() macros can be used to
achieve simpler race-free callout semantics in many situations.
callout_stop(), except that if the callout being stopped is currently
in progress, it blocks attempts to reset the callout and waits until the
callout is completed before it returns.
This makes it possible to clean up callout-using code safely, e.g.,
without potentially freeing memory which is still being used by a callout.
Reviewed by: mux, gallatin, rwatson, jhb
callout lock while the callout is happening. So the serialization
that I thought was happening isn't. Therefore, remove the part of the
bugs that says this. Leave in the other bug as it is very hard to
work around (impossible?).
Fix various typos.
Also note that timeout/untimeout are considered to be the old interface and
the callout interface should be used insetad.
Submitted by: bde (first two) and wollman (third)
callout has finished or is in progress. Also document that the
locking of the callout code for FreeBSD 5 has eliminated the 'or is in
progress' clause as a possibility and that such elimination is an
accident of the implementation and shouldn't be relied upon.
cd src/share; find man[1-9] -type f|xargs perl -pi -e 's/[ \t]+$//'
BTW, what editors are the culprits? I'm using vim and it shows
me whitespace at EOL in troff files with a thick blue block...
Reviewed by: Silence from cvs diff -b
MFC after: 7 days
spl0) and some bitrot (the not-so-new callout_init/stop/reset functions
were not mentioned; the callout_activate/deactivate/pending macros are
still not mentioned).
Submitted by: mostly by jlemon
