will only display sleep mutexes held by the current process.
- Clean up some nits in the witness_display() function and add a ddb
command 'show witness' that dumps the hierarchy and order lists to the
console.
- Use queue(3) macros where appropriate.
- Resort the spin lock order list so that "com" is before "sched_lock".
Also, add appropriate #ifdef's around SMP and i386-specific mutexes.
- Add two new mutexes used to protect the ithread lists and tables to the
order list.
Requested by: bde (1)
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)
mtx right now as it makes debugging harder. When we are in optimizing
mode, we can revisit this.
- Fix the KTR trace messages to use %p rather than 0x%p to avoid duplicate
0x's in KTR output.
- During witness_fixup, release Giant so that witness doesn't get confused.
Also, grab all_mtx while walking the list of mutexes.
- Remove w_sleep and w_recurse. Instead, perform checks on mutexes using
the mutex's mtx_flags field.
- Allow debug.witness_ddb and debug.witness_skipspin to be set from the
loader.
- Add Giant to the front of existing order_list entries to help ensure
Giant is always first.
- Add an order entry for the various proc locks. Note that this only
helps keep proc in order mostly as the allproc and proctree mutexes are
only obtained during a lockmgr operation on the specified mutex.
inline functions non-inlined. Hide parts of the mutex implementation that
should not be exposed.
Make sure that WITNESS code is not executed during boot until the mutexes
are fully initialized by SI_SUB_MUTEX (the original motivation for this
commit).
Submitted by: peter
initialization until after malloc() is safe to call, then iterate through
all mutexes and complete their initialization.
This change is necessary in order to avoid some circular bootstrapping
dependencies.
All calls to mtx_init() for mutexes that recurse must now include
the MTX_RECURSE bit in the flag argument variable. This change is in
preparation for an upcoming (further) mutex API cleanup.
The witness code will call panic() if a lock is found to recurse but
the MTX_RECURSE bit was not set during the lock's initialization.
The old MTX_RECURSE "state" bit (in mtx_lock) has been renamed to
MTX_RECURSED, which is more appropriate given its meaning.
The following locks have been made "recursive," thus far:
eventhandler, Giant, callout, sched_lock, possibly some others declared
in the architecture-specific code, all of the network card driver locks
in pci/, as well as some other locks in dev/ stuff that I've found to
be recursive.
Reviewed by: jhb
functions. If this flag is set, then no KTR log messages are issued.
This is useful for blocking excessive logging, such as with the internal
mutex used by the witness code.
- Use MTX_QUIET on all of the mtx_enter/exit operations on the internal
mutex used by the witness code.
- If we are in a panic, don't do witness checks in witness_enter(),
witness_exit(), and witness_try_enter(), just return.
held and panic if so (conditional on witness).
- Change witness_list to return the number of locks held so this is easier.
- Add kern/syscalls.c to the kernel build if witness is defined so that the
panic message can contain the name of the offending system call.
- Add assertions that Giant and sched_lock are not held when returning from
a system call, which were missing for alpha and ia64.
depend on MUTEX_DEBUG. The MUTEX_DEBUG option turns on extra assertions
and checks to verify that mutexes themselves are implemented properly.
The WITNESS option uses extra checks and diagnostics to verify that other
code is using mutexes properly.
- Use a better test for determining when a process is running.
- Convert some checks to assertions.
- Remove unnecessary tests.
- Save the priority before acquiring a mutex rather than in msleep(9).
- Use the mutex in hardclock to ensure no races between it and
softclock.
- Make softclock be INTR_MPSAFE and provide a flag,
CALLOUT_MPSAFE, which specifies that a callout handler does not
need giant. There is still no way to set this flag when
regstering a callout.
Reviewed by: -smp@, jlemon
may block on a mutex while on the sleep queue without corrupting
it.
- Move dropping of Giant to after the acquire of sched_lock.
Tested by: John Hay <jhay@icomtek.csir.co.za>
jhb
acquire Giant as needed in functions that call mi_switch(). The releases
need to be done outside of the sched_lock to avoid potential deadlocks
from trying to acquire Giant while interrupts are disabled.
Submitted by: witness
it can function before malloc(9) is up and running.
- Add two new options WITNESS_DDB and WITNESS_SKIPSPIN. If WITNESS_SKIPSPIN
is enabled, then spin mutexes are ignored by the WITNESS code. If
WITNESS_DDB is turned on and DDB is compiled into the kernel, then the
kernel will drop into DDB when either a lock hierarchy violation occurs
or mutexes are held when going to sleep.
- Add some new sysctls:
debug.witness_ddb is a read-write sysctl that corresponds to WITNESS_DDB.
The kernel option merely changes the default value to on at boot.
debug.witness_skipspin is a read-only sysctl that one can use to determine
if the kernel was compiled with WITNESS_SKIPSPIN.
- Wipe out the BSD/OS-specific lock order lists. We get to build our own
lists now as we add mutexes to the kernel.
reducues the maintenance load for the mutex code. The only MD portions
of the mutex code are in machine/mutex.h now, which include the assembly
macros for handling mutexes as well as optionally overriding the mutex
micro-operations. For example, we use optimized micro-ops on the x86
platform #ifndef I386_CPU.
- Change the behavior of the SMP_DEBUG kernel option. In the new code,
mtx_assert() only depends on INVARIANTS, allowing other kernel developers
to have working mutex assertiions without having to include all of the
mutex debugging code. The SMP_DEBUG kernel option has been renamed to
MUTEX_DEBUG and now just controls extra mutex debugging code.
- Abolish the ugly mtx_f hack. Instead, we dynamically allocate
seperate mtx_debug structures on the fly in mtx_init, except for mutexes
that are initiated very early in the boot process. These mutexes
are declared using a special MUTEX_DECLARE() macro, and use a new
flag MTX_COLD when calling mtx_init. This is still somewhat hackish,
but it is less evil than the mtx_f filler struct, and the mtx struct is
now the same size with and without mutex debugging code.
- Add some micro-micro-operation macros for doing the actual atomic
operations on the mutex mtx_lock field to make it easier for other archs
to override/optimize mutex ops if needed. These new tiny ops also clean
up the code in some places by replacing long atomic operation function
calls that spanned 2-3 lines with a short 1-line macro call.
- Don't call mi_switch() from mtx_enter_hard() when we block while trying
to obtain a sleep mutex. Calling mi_switch() would bogusly release
Giant before switching to the next process. Instead, inline most of the
code from mi_switch() in the mtx_enter_hard() function. Note that when
we finally kill Giant we can back this out and go back to calling
mi_switch().
macros that expand to pass filename and line number information. This is
necessary since we're using inline functions instead of macros now.
Add const to the filename pointers passed througout the mtx and witness
code.
include:
* Mutual exclusion is used instead of spl*(). See mutex(9). (Note: The
alpha port is still in transition and currently uses both.)
* Per-CPU idle processes.
* Interrupts are run in their own separate kernel threads and can be
preempted (i386 only).
Partially contributed by: BSDi (BSD/OS)
Submissions by (at least): cp, dfr, dillon, grog, jake, jhb, sheldonh
