Use this instead of DEBUG_LASTREQS to decide whether to log lock
requests.
MFS:
vinumlock: Catch a potential race condition where one process is
waiting for a lock, and between the time it is woken and
it retries the lock, another process gets it and places it
in the first entry in the table.
This problem has not been observed, but it's possible, and
it's easy enough to fix.
Submitted by: tegge
vinumunlock: Catch a real bug capable of hanging a system. When
releasing a lock, vinumunlock() called wakeup_one. This
caused wakeups to sometimes get lost. After due
consideration, we think that this is due to the fact that
you can't guarantee that some other process is also
waiting on the same address. This makes wakeup_one a
very dangerous function to use.
mtx_enter(lock, type) becomes:
mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)
similarily, for releasing a lock, we now have:
mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.
The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.
Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:
MTX_QUIET and MTX_NOSWITCH
The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:
mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.
Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.
Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.
Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.
Finally, caught up to the interface changes in all sys code.
Contributors: jake, jhb, jasone (in no particular order)
Rewrite lockrange and unlockrange. The lock table is now a fixed
size, so there is no possibility for race conditions when expanding.
The current size (256 locked ranges) should be large enough that it
makes no sense to expand it. To do expansion right would require
quiescing the plex (requiring at least 256 I/O completions), and the
performance implications are horrendous.
Add a mutex per plex for accessing the lock table.
Based on analysis by: tegge
lockrange: correctly expand rangelock struct, including expanding a
null struct. Previously lockrange would attempt to lock a
NULL pointer under these circumstances.
Reported-by: Ian Freislich <iang@uunet.co.za>
solve some data integrity problems that have been reported with
degraded RAID-5 plexes.
Reported-by: Bernd Walter <ticso@cicely.de>
Remy Nonnenmacher <remy@synx.com>
kernel as a pseudo-device. The changes were:
- #ifdef DEBUG -> #ifdef VINUMDEBUG
- opt_vinum.h for holding above config variable
- Fixing up a few stray problems where DEBUG wasn't optional.
- config.c -> vinumconfig.c (there's already a config.o)
- Other *.c -> vinum*.c (wasn't strictly necessary, but done in case we end
up with something else conflicting later on and we might have to have yet
more repository copies of files).
- include file paths fixups.. (ie: get them all from the kernel tree
instead of partly from the kernel and partly from /usr/include/machine)
I've spoken with Greg about this.. I hope this doesn't mess him around
too much..
