things allows variable length messages to be easily supported.
- Extend KPI with alq_writen() and alq_getn() to support variable length
messages, which is enabled at ALQ creation time depending on the
arguments passed to alq_open(). Also add variants of alq_open() and
alq_post() that accept a flags argument. The KPI is still fully
backwards compatible and shouldn't require any change in ALQ consumers
unless they wish to utilise the new features.
- Introduce the ALQ_NOACTIVATE and ALQ_ORDERED flags to allow ALQ consumers
to have more control over IO scheduling and resource acquisition
respectively.
- Strengthen invariants checking.
- Document ALQ changes in ALQ(9) man page.
Sponsored by: FreeBSD Foundation
Reviewed by: gnn, jeff, rpaulo, rwatson
MFC after: 1 month
Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.
Reviewed by: ru
Approved by: philip, ed (mentors)
In the current code, the locking is completely broken and may lead
easilly to deadlocks. Fix it by using the proc_mtx, linked to the
suspending thread, as lock for the operation. Keep using the
thread_lock for setting and reading the flag even if it is not entirely
necessary (atomic ops may do it as well, but this way the code is more
readable).
- Fix a deadlock within kthread_suspend().
The suspender should not sleep on a different channel wrt the suspended
thread, or, otherwise, the awaker should wakeup both. Uniform the
interface to what the kproc_* counterparts do (sleeping on the same
channel).
- Change the kthread_suspend_check() prototype.
kthread_suspend_check() always assumes curthread and must only refer to
it, so skip the thread pointer as it may be easilly mistaken.
If curthread is not a kthread, the system will panic.
In collabouration with: jhb
Tested by: Giovanni Trematerra
<giovanni dot trematerra at gmail dot com>
MFC: 2 weeks
if_initname().
- Document if_drv_flags and replace references to IFF_(RUNNING|OACTIVE)
with references to IFF_DRV_(RUNNING|OACTIVE).
- Complete truncated sentence in the description of if_transmit by copying
from the description in if_qflush.
- Add missing line breaks for translators.
Reviewed by: brooks (1)
MFC after: 3 days
<sys/proc.h>.
- Add RETURN VALUES and ERROR sections for namei()'s error return values.
- Add a missing link to NDHASGIANT.9.
PR: docs/142815, docs/142816
Submitted by: Lachlan Kang (1, 2)
MFC after: 3 days
While the name is pretentious, a good explanation of its targets is
reported in this 17 months old presentation e-mail:
http://lists.freebsd.org/pipermail/freebsd-arch/2008-August/008452.html
In order to implement it, the sq_type in sleepqueues is mandatory and not
only compiled along with INVARIANTS option. Additively, a new sleepqueue
function, sleepq_type() is added, returning the type of the sleepqueue
linked to a wchan.
Three new sysctls are added in order to configure the thread:
debug.deadlkres.slptime_threshold
debug.deadlkres.blktime_threshold
debug.deadlkres.sleepfreq
rappresenting the thresholds for sleep and block time that will lead to
a deadlock matching (when exceeded), while the sleepfreq rappresents the
number of seconds between 2 consecutive thread runnings.
In order to enable the deadlock resolver thread recompile your kernel
with the option DEADLKRES.
Reviewed by: jeff
Tested by: pho, Giovanni Trematerra
Sponsored by: Nokia Incorporated, Sandvine Incorporated
MFC after: 2 weeks
sxlock, via the sx_{s, x}lock_sig() interface, or plain lockmgr), will
leave the waiters flag on forcing the owner to do a wakeup even when if
the waiter queue is empty.
That operation may lead to a deadlock in the case of doing a fake wakeup
on the "preferred" (based on the wakeup algorithm) queue while the other
queue has real waiters on it, because nobody is going to wakeup the 2nd
queue waiters and they will sleep indefinitively.
A similar bug, is present, for lockmgr in the case the waiters are
sleeping with LK_SLEEPFAIL on. In this case, even if the waiters queue
is not empty, the waiters won't progress after being awake but they will
just fail, still not taking care of the 2nd queue waiters (as instead the
lock owned doing the wakeup would expect).
In order to fix this bug in a cheap way (without adding too much locking
and complicating too much the semantic) add a sleepqueue interface which
does report the actual number of waiters on a specified queue of a
waitchannel (sleepq_sleepcnt()) and use it in order to determine if the
exclusive waiters (or shared waiters) are actually present on the lockmgr
(or sx) before to give them precedence in the wakeup algorithm.
This fix alone, however doesn't solve the LK_SLEEPFAIL bug. In order to
cope with it, add the tracking of how many exclusive LK_SLEEPFAIL waiters
a lockmgr has and if all the waiters on the exclusive waiters queue are
LK_SLEEPFAIL just wake both queues.
The sleepq_sleepcnt() introduction and ABI breakage require
__FreeBSD_version bumping.
Reported by: avg, kib, pho
Reviewed by: kib
Tested by: pho
handlers. This is primarily intended as a way to allow devices that use
multiple interrupts (e.g. MSI) to meaningfully distinguish the various
interrupt handlers.
- Add a new BUS_DESCRIBE_INTR() method to the bus interface to associate
a description with an active interrupt handler setup by BUS_SETUP_INTR.
It has a default method (bus_generic_describe_intr()) which simply passes
the request up to the parent device.
- Add a bus_describe_intr() wrapper around BUS_DESCRIBE_INTR() that supports
printf(9) style formatting using var args.
- Reserve MAXCOMLEN bytes in the intr_handler structure to hold the name of
an interrupt handler and copy the name passed to intr_event_add_handler()
into that buffer instead of just saving the pointer to the name.
- Add a new intr_event_describe_handler() which appends a description string
to an interrupt handler's name.
- Implement support for interrupt descriptions on amd64 and i386 by having
the nexus(4) driver supply a custom bus_describe_intr method that invokes
a new intr_describe() MD routine which in turn looks up the associated
interrupt event and invokes intr_event_describe_handler().
Requested by: many
Reviewed by: scottl
MFC after: 2 weeks
