Problem:
selwakeup required calling pfind which would cause lock order
reversals with the allproc_lock and the per-process filedesc lock.
Solution:
Instead of recording the pid of the select()'ing process into the
selinfo structure, actually record a pointer to the thread. To
avoid dereferencing a bad address all the selinfo structures that
are in use by a thread are kept in a list hung off the thread
(protected by sellock). When a selwakeup occurs the selinfo is
removed from that threads list, it is also removed on the way out
of select or poll where the thread will traverse its list removing
all the selinfos from its own list.
Problem:
Previously the PROC_LOCK was used to provide the mutual exclusion
needed to ensure proper locking, this couldn't work because there
was a single condvar used for select and poll and condvars can
only be used with a single mutex.
Solution:
Introduce a global mutex 'sellock' which is used to provide mutual
exclusion when recording events to wait on as well as performing
notification when an event occurs.
Interesting note:
schedlock is required to manipulate the per-thread TDF_SELECT
flag, however if given its own field it would not need schedlock,
also because TDF_SELECT is only manipulated under sellock one
doesn't actually use schedlock for syncronization, only to protect
against corruption.
Proc locks are no longer used in select/poll.
Portions contributed by: davidc
hw.midi.debug and hw.midi.seq.debug to 1 to enable debug log.
- Make debug messages human-frendly.
- Implement /dev/music.
- Add a timer engine required by /dev/music.
- Fix nonblocking I/O.
- Fix the numbering of midi and synth devices.
- Move from msleep/wakeup to condvar.
- Return either zero or a positive errno value from a function.
Return additional result via references.
- Unify the typedef of callback functions.
If you ever want to run midi(4) out of the giant lock, uncomment
MIDI_OUTOFGIANT in midi.h. Confirmed to work for csamidi with WITNESS
and INVARIANTS.
- midi_info, midi_open and seq_info are now tailqs, allowing arbitrary
numbers of devices to be configured.
- Do not send an active sensing message to reset midi modules.
- Clone /dev/sequencer*. /dev/sequencer0 and /dev/sequencer are generated
upon initialization.
cloning infrastructure standard in kern_conf. Modules are now
the same with or without devfs support.
If you need to detect if devfs is present, in modules or elsewhere,
check the integer variable "devfs_present".
This happily removes an ugly hack from kern/vfs_conf.c.
This forces a rename of the eventhandler and the standard clone
helper function.
Include <sys/eventhandler.h> in <sys/conf.h>: it's a helper #include
like <sys/queue.h>
Remove all #includes of opt_devfs.h they no longer matter.
(I had been busy for my own research activity until the last weekend)
Supported devices:
SB Midi Port (sbc + midi)
SB OPL3 (sbc + midi)
16550 UART (midi, needs a trick in your hint)
CS461x Midi Port (csa + midi)
OSS-compatible sequencer (seq)
Supported playing software:
playmidi (We definitely need more)
Notes:
/dev/midistat now reports installed midi drivers. /dev/sndstat reports
only pcm drivers. We need the new name(pcmstat?).
EMU8000(SB AWE) does not sound yet but does get probed so that the OPL3
synth on an AWE card works.
TODO:
MSS/PCI bridge drivers
Midi-tty interface to support general serial devices
Modules
