The scope of these callbacks is primarily to support actions that affect the
taskqueue's thread environments. They are entirely optional, and
consequently are introduced as a new API: taskqueue_set_callback().
This interface allows the caller to specify that a taskqueue requires a
callback and optional context pointer for a given callback type.
The callback types included in this commit can be used to register a
constructor and destructor for thread-local storage using osd(9). This
allows a particular taskqueue to define that its threads require a specific
type of TLS, without the need for a specially-orchestrated task-based
mechanism for startup and shutdown in order to accomplish it.
Two callback types are supported at this point:
- TASKQUEUE_CALLBACK_TYPE_INIT, called by every thread when it starts, prior
to processing any tasks.
- TASKQUEUE_CALLBACK_TYPE_SHUTDOWN, called by every thread when it exits,
after it has processed its last task but before the taskqueue is
reclaimed.
While I'm here:
- Add two new macros, TQ_ASSERT_LOCKED and TQ_ASSERT_UNLOCKED, and use them
in appropriate locations.
- Fix taskqueue.9 to mention taskqueue_start_threads(), which is a required
interface for all consumers of taskqueue(9).
Reviewed by: kib (all), eadler (taskqueue.9), brd (taskqueue.9)
Approved by: ken (mentor)
Sponsored by: Spectra Logic
MFC after: 1 month
taskqueue_enqueue_timeout(). Do not rearm the callout if it is
already armed and the ticks is negative. Otherwise rearm it to fire
in abs(ticks) ticks in the future.
The intended use is to call taskqueue_enqueue_timeout() for the given
timeout_task with the same negative ticks argument. As result, the
task is scheduled to execute not further than abs(ticks) ticks in
future, and the consequent enqueues are coalesced until the already
scheduled task is finished.
Reviewed by: rwatson
Tested by: Markus Gebert <markus.gebert@hostpoint.ch>
MFC after: 2 weeks
If it overflows before the taskqueue can run, the task will be
re-added to the taskqueue and cause a loop in the task list.
Reported by: Arnaud Lacombe <lacombar@gmail.com>
Submitted by: Ryan Stone <rysto32@gmail.com>
Reviewed by: jhb
Approved by: re (kib)
MFC after: 1 day
mechanism. The caller may specify a timeout in ticks after which the
task will be scheduled.
Sponsored by: The FreeBSD Foundation
Reviewed by: jeff, jhb
MFC after: 1 month
tq_name was used write-only and besides it was just a pointer, so it
could point to some garbage in a temporary buffer that's gone.
This change shouldn't change KPI/KBI as struct taskqueue is private to
subr_taskqueue.c.
If we find a need for tq_name it can be resurrected at any moment.
taskqueue_create() interface is preserved for this purpose.
Suggested by: jhb
MFC after: 10 days
taskqueues, more than one task can be running simultaneously.
Also make taskqueue_run(9) static to the file, since there are no
consumers in the base kernel and the function signature needs to change
with this fix.
Remove mention of taskqueue_run(9) and taskqueue_run_fast(9) from the
taskqueue(9) man page.
Reviewed by: jhb
Approved by: zml (mentor)
via %s
Most of the cases looked harmless, but this is done for the sake of
correctness. In one case it even allowed to drop an intermediate buffer.
Found by: clang
MFC after: 2 week
ta_func may free the task structure, so no references to its members
are valid after the handler has been called. Using a per-queue member
and having waits longer than strictly necessary was suggested by jhb.
Submitted by: Matthew Fleming <matthew.fleming@isilon.com>
Reviewed by: zml, jhb
taskqueue_drain(9) will not correctly detect whether a task is
currently running. The check is against a field in the taskqueue
struct, but for a threaded queue with more than one thread, multiple
threads can simultaneously be running a task, thus stomping over the
tq_running field.
Submitted by: Matthew Fleming <matthew.fleming@isilon.com>
Reviewed by: jhb
Approved by: dfr (mentor)
td_name[] arrays are actually MAXCOMLEN + 1 in size and a few places that
created shadow copies of these arrays were just using MAXCOMLEN.
- Prefer using sizeof() of an array type to explicit constants for the
array length in a few places.
- Ensure that all of p_comm[] and td_name[] is always zero'd during
execve() to guard against any possible information leaks. Previously
trailing garbage in p_comm[] could be leaked to userland in ktrace
record headers via td_name[].
Reviewed by: bde
replace it with wrappers around our taskqueue(9).
To make it possible implement taskqueue_member() function which returns 1
if the given thread was created by the given taskqueue.
Approved by: re (kib)
the owner of a queue to block and unblock execution of the tasks in the
queue while allowing tasks to continue to be added queue. Combining this
with taskqueue_drain() allows a queue to be safely disabled. The unblock
function may run (or schedule to run) the queue when it is called, just as
calling taskqueue_enqueue() would.
Reviewed by: jhb, sam
to kproc_xxx as they actually make whole processes.
Thos makes way for us to add REAL kthread_create() and friends
that actually make theads. it turns out that most of these
calls actually end up being moved back to the thread version
when it's added. but we need to make this cosmetic change first.
I'd LOVE to do this rename in 7.0 so that we can eventually MFC the
new kthread_xxx() calls.
- Use thread_lock() rather than sched_lock for per-thread scheduling
sychronization.
- Use the per-process spinlock rather than the sched_lock for per-process
scheduling synchronization.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
setrunqueue() was mostly empty. The few asserts and thread state
setting were moved to the individual schedulers. sched_add() was
chosen to displace it for naming consistency reasons.
- Remove adjustrunqueue, it was 4 lines of code that was ifdef'd to be
different on all three schedulers where it was only called in one place
each.
- Remove the long ifdef'd out remrunqueue code.
- Remove the now redundant ts_state. Inspect the thread state directly.
- Don't set TSF_* flags from kern_switch.c, we were only doing this to
support a feature in one scheduler.
- Change sched_choose() to return a thread rather than a td_sched. Also,
rely on the schedulers to return the idlethread. This simplifies the
logic in choosethread(). Aside from the run queue links kern_switch.c
mostly does not care about the contents of td_sched.
Discussed with: julian
- Move the idle thread loop into the per scheduler area. ULE wants to
do something different from the other schedulers.
Suggested by: jhb
Tested on: x86/amd64 sched_{4BSD, ULE, CORE}.
stopped before adjusting their priority and setting them on the run
q so they cannot race for resources (pointed out by njl).
While here add a console printf on thread create fails; otherwise
noone may notice (e.g. return value is always 0 and caller has no
way to verify).
Reviewed by: jhb, scottl
MFC after: 2 weeks
if the specified priority is zero. This avoids a race where the calling
thread could read a snapshot of it's current priority, then a different
thread could change the first thread's priority, then the original thread
would call sched_prio() inside msleep() undoing the change made by the
second thread. I used a priority of zero as no thread that calls msleep()
or tsleep() should be specifying a priority of zero anyway.
The various places that passed 'curthread->td_priority' or some variant
as the priority now pass 0.
failing, print a message when we fail for some reason as most callers do
not check the return value (e.g. 'cuz they're called from SYSINIT)
Reviewed by: scottl
MFC after: 1 week
taskqueue_start_threads(struct taskqueue **, int count, int pri,
const char *name, ...);
This allows the creation of 1 or more threads that will service a single
taskqueue. Also rework the taskqueue_create() API to remove the API change
that was introduced a while back. Creating a taskqueue doesn't rely on
the presence of a process structure, and the proc mechanics are much better
encapsulated in taskqueue_start_threads(). Also clean up the
taskqueue_terminate() and taskqueue_free() functions to safely drain
pending tasks and remove all associated threads.
The TASKQUEUE_DEFINE and TASKQUEUE_DEFINE_THREAD macros have been changed
to use the new API, but drivers compiled against the old definitions will
still work. Thus, recompiling drivers is not a strict requirement.
fast taskqueues. The following have been added:
TASKQUEUE_FAST_DEFINE() - create a global task queue.
an arbitrary execution context.
TASKQUEUE_FAST_DEFINE_THREAD() - create a global taskqueue that uses a
dedicated kthread.
taskqueue_create_fast() - create a local/private taskqueue.
These are all complimentary of the standard taskqueue functions. They are
primarily useful for fast interrupt handlers that can only use spinlock for
synchronization.
I personally think that the taskqueue API is starting to get too narrow and
hairy, but fixing it will require a major redesign on the API. Such a
redesign would be good but would break compatibility with FreeBSD 6.x, so
it really isn't desirable at this time.
Submitted by: sam
a new entry in the taskqueue struct each time it wakes up to see if it
should terminate
o adjust TASKQUEUE_DEFINE_THREAD & co. to record the thread/proc identity for
the shutdown rendezvous
o replace wakeup after adding a task to a queue with wakeup_one; this helps
queues where multiple threads are used to service tasks (e.g. acpi)
o remove NULL check of tq_enqueue method; it should never be NULL
Reviewed by: dfr, njl
modify-after-free races when the task structure is malloc'd
o shrink task structure by removing ta_flags (no longer needed with
avoid fix) and combining ta_pending and ta_priority
Reviewed by: dwhite, dfr
MFC after: 4 days
the queue has been removed from the global taskqueue_queues list. This
removes the need for the draining queue hack.
- Allow taskqueue_run() to be called with the taskqueue mutex held. It
can still be called without the lock for API compatiblity. In that case
it will acquire the lock internally.
- Don't lock the individual queue mutex in taskqueue_find() until after the
strcmp as the global queues mutex is sufficient for the strcmp.
- Simplify taskqueue_thread_loop() now that it can hold the lock across
taskqueue_run().
Submitted by: bde (mostly)
Instead of creating a mutex that we msleep on but don't actually lock when
doing the corresponding wakeup(), in the kthread, lock the mutex associated
with our taskqueue and msleep while the queue is empty. Assert that the
queue is locked when the callback function is called to wake the kthread.
