struct callout_cpu. From the comment in the file:
+ * There is one struct callout_cpu per cpu, holding all relevant
+ * state for the callout processing thread on the individual CPU.
+ * In particular:
+ * cc_ticks is incremented once per tick in callout_cpu().
+ * It tracks the global 'ticks' but in a way that the individual
+ * threads should not worry about races in the order in which
+ * hardclock() and hardclock_cpu() run on the various CPUs.
+ * cc_softclock is advanced in callout_cpu() to point to the
+ * first entry in cc_callwheel that may need handling. In turn,
+ * a softclock() is scheduled so it can serve the various entries i
+ * such that cc_softclock <= i <= cc_ticks .
Together with a smaller patch committed in september, this fixes a
bug that affects 8.0 with apps that rely on callouts to fire exactly
in the number of ticks specified (qemu among them).
Right now, callouts in 8.0 fire one tick late.
This was discussed in september with JeffR and jhb
MFC after: 3 days
The problem was introduced in SVN 180608/ rev 1.114 and affects
all users of callout_reset() (including select, usleep, setitimer).
A better fix probably involves replicating 'ticks' in the
struct callout_cpu; this commit is just a temporary thing so that
we can MFC it after a suitable test time and RE approval.
MFC after: 3 days
pointers to the callout handler just before and just after the callout
it invoked. I attempted to do this in a manner congruent to tracing in
Solaris's callout mechanism, but couldn't quite use the same names due
to convention and syntax differences.
Example DTrace script to generate a distribution graph of callout
execution times:
callout_execute:::callout_start
{
self->cstart = timestamp;
}
callout_execute:::callout_end
{
@length = quantize(timestamp - self->cstart);
}
Reviewed by: jb
MFC after: 3 days
"ticks" goes negative. This breaks the signed comparison in softclock.
This causes sleep() to never wake up, tcp to stop, etc etc. This is
bad(TM). Use the SEQ_LT() method from tcp's sequence number comparisons.
- When a tick occurs on a cpu, iterate from cs_softticks until ticks.
The per-cpu tick processing happens asynchronously with the actual
adjustment of the 'ticks' variable. Sometimes the results may
be visible before the local call and sometimes after. Previously this
could cause a one tick window where we didn't evaluate the bucket.
- In softclock fetch curticks before incrementing cc_softticks so we
don't skip insertions which were made for the current time.
Sponsored by: Nokia
- Move callout thread creation from kern_intr.c to kern_timeout.c
- Call callout_tick() on every processor via hardclock_cpu() rather than
inspecting callout internal details in kern_clock.c.
- Remove callout implementation details from callout.h
- Package up all of the global variables into a per-cpu callout structure.
- Start one thread per-cpu. Threads are not strictly bound. They prefer
to execute on the native cpu but may migrate temporarily if interrupts
are starving callout processing.
- Run all callouts by default in the thread for cpu0 to maintain current
ordering and concurrency guarantees. Many consumers may not properly
handle concurrent execution.
- The new callout_reset_on() api allows specifying a particular cpu to
execute the callout on. This may migrate a callout to a new cpu.
callout_reset() schedules on the last assigned cpu while
callout_reset_curcpu() schedules on the current cpu.
Reviewed by: phk
Sponsored by: Nokia
code.
The bug:
There exists a race condition for timeout/untimeout(9) due to the
way that the softclock thread dequeues timeouts.
The softclock thread sets the c_func and c_arg of the callout to
NULL while holding the callout lock but not Giant. It then drops
the callout lock and acquires Giant.
It is at this point where untimeout(9) on another cpu/thread could
be called.
Since c_arg and c_func are cleared, untimeout(9) does not touch the
callout and returns as if the callout is canceled.
The softclock then tries to acquire Giant and likely blocks due to
the other cpu/thread holding it.
The other cpu/thread then likely deallocates the backing store that
c_arg points to and finishes working and hence drops Giant.
Softclock resumes and acquires giant and calls the function with
the now free'd c_arg and we have corruption/crash.
The fix:
We need to track curr_callout even for timeout(9) (LOCAL_ALLOC)
callouts. We need to free the callout after the softclock processes
it to deal with the race here.
Obtained from: Juniper Networks, iedowse
Reviewed by: jhb, iedowse
MFC After: 2 weeks.
sched_sleep(). This removes extra thread_lock() acquisition and
allows the scheduler to decide what to do with the static boost.
- Change the priority arguments to cv_* to match sleepq/msleep/etc.
where 0 means no priority change. Catch -1 in cv_broadcastpri() and
convert it to 0 for now.
- Set a flag when sleeping in a way that is compatible with swapping
since direct priority comparisons are meaningless now.
- Add a sysctl to ule, kern.sched.static_boost, that defaults to on which
controls the boost behavior. Turning it off gives better performance
in some workloads but needs more investigation.
- While we're modifying sleepq, change signal and broadcast to both
return with the lock held as the lock was held on enter.
Reviewed by: jhb, peter
done in consumers code: using locks properties is much more appropriate.
Fix current code doing these bogus checks.
Note: Really, callout are not usable by all !(LC_SPINLOCK | LC_SLEEPABLE)
primitives like rmlocks doesn't implement the generic lock layer
functions, but they can be equipped for this, so the check is still
valid.
Tested by: matteo, kris (earlier version)
Reviewed by: jhb
while the global callout spinlock is not held, and can lead to PF#.
Reported by: dougb, Mark Atkinson <atkin901 at yahoo dot com>
Tested by: dougb
Diagnosed by: jhb
rwlocks in conjuction with callouts. The function does basically what
callout_init_mtx() alredy does with the difference of using a rwlock
as extra argument.
CALLOUT_SHAREDLOCK flag can be used, now, in order to acquire the lock only
in read mode when running the callout handler. It has no effects when used
in conjuction with mtx.
In order to implement this, underlying callout functions have been made
completely lock type-unaware, so accordingly with this, sysctl
debug.to_avg_mtxcalls is now changed in the generic
debug.to_avg_lockcalls.
Note: currently the allowed lock classes are mutexes and rwlocks because
callout handlers run in softclock swi, so they cannot sleep and they
cannot acquire sleepable locks like sx or lockmgr.
Requested by: kmacy, pjd, rwatson
Reviewed by: jhb
the callout_lock spin lock and the sleepqueue spin locks. In the fix,
callout_drain() has to drop the callout_lock so it can acquire the
sleepqueue lock. The state of the callout can change while the
callout_lock is held however (for example, it can be rescheduled via
callout_reset()). The previous code assumed that the only state change
that could happen is that the callout could finish executing. This change
alters callout_drain() to effectively restart and recheck everything
after it acquires the sleepqueue lock thus handling all the possible
states that the callout could be in after any changes while callout_lock
was dropped.
Approved by: re (kensmith)
Tested by: kris
could lead to a deadlock).
- sleepq_set_timeout acquires callout_lock (via callout_reset()) only
with sleepq chain lock held
- msleep_spin in _callout_stop_safe lock the sleepqueue chain with
callout_lock held
In order to solve this don't use msleep_spin in _callout_stop_safe() but
use directly sleepqueues as inline msleep_spin code. Rearrange the
wakeup path in order to have it consistent too.
Reported by: kris (via stress2 test suite)
Tested by: Timothy Redaelli <drizzt@gufi.org>
Reviewed by: jhb
Approved by: jeff (mentor)
Approved by: re
removals, including failures, into the callwheel.
XXX: Most of the CTR() macros are called with callout_lock spin mutex
held, thus won't be logged into file, if KTR_ALQ is used. Moving the
CTR() macros out from the spinlocked code would require copying of all
arguments. I'm too lazy to do this.
callout_drain() logic. We no longer need a separate non-spin mutex to
do sleep/wakeup with, instead we can now just use the one spin mutex to
manage all the callout functionality.
list, set `curr_callout' to NULL. This ensures that we won't attempt
to cancel the current callout if the original callout structure
gets recycled while we wait to acquire Giant.
This is reported to fix an intermittent syscons problem that was
introduced by revision 1.96.
callout is first initialised, using a new function callout_init_mtx().
The callout system will acquire this mutex before calling the callout
function and release it on return.
In addition, the callout system uses the mutex to avoid most of the
complications and race conditions inherent in asynchronous timer
facilities, so mutex-protected callouts have much simpler semantics.
As long as the mutex is held when invoking callout_stop() or
callout_reset(), then these functions will guarantee that the callout
will be stopped, even if softclock() had already begun to process
the callout.
Existing Giant-locked callouts will automatically pick up the new
race-free semantics. This should close a number of race conditions
in the USB code and probably other areas of the kernel too.
There should be no change in behaviour for "MP-safe" callouts; these
still need to use the techniques mentioned in timeout(9) to avoid
race conditions.
callout_reset rather than calling callout_stop. This results in a few
lines of code duplication, but it provides a significant performance
improvement because it avoids recursing on callout_lock.
Requested by: rwatson
2. Document that this means that kernel modules must be rebuilt.
3. While I'm here, fix my sorting error in callout.h
Requested by: many [1], scottl [2], bde [3]
Remove spurious whitespace, add indent protection, fix punctuation,
remove initialization of static variables to zero, put wakeup_ctr
and wakeup_needed in the correct order. (reported by bde)
This doesn't fix all the style bugs I introduced, but the remaining
style bugs make it easier for me to understand what I did here.
callout_stop(), except that if the callout being stopped is currently
in progress, it blocks attempts to reset the callout and waits until the
callout is completed before it returns.
This makes it possible to clean up callout-using code safely, e.g.,
without potentially freeing memory which is still being used by a callout.
Reviewed by: mux, gallatin, rwatson, jhb
functions less noisy: We printf if a new function took longer than
the previous record holder, or of the previous record holder took
more than twice as long as the current record.
deleted in 1.81. Increase the initial timeout limit to 2ms to
eliminate spurious messages of excessive timeouts in the NFS
client code.
Requested by: Poul-Henning Kamp <phk@phk.freebsd.dk>
Requested by: Mike Silbersack <silby@silby.com>
Requested by: Sam Leffler <sam@errno.com>
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
timeout callwheel and buffer cache, out of the platform specific areas
and into the machine independant area. i386 and alpha adjusted here.
Other cpus can be fixed piecemeal.
Reviewed by: freebsd-smp, jake
removing the callout entry, return 1. If callout_stop() fails to remove
the callout entry because it is currently executing or has already been
executed, then the function returns 0. The idea was obtained from BSD/OS,
however, BSD/OS changed untimeout(), and I've just changed callout_stop()
to be more conservative.
Obtained from: BSD/OS
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)
- 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
are in softclock() for a long time. The old code already did an
splx()/slphigh() pair here, I just missed adding in the equivalent mutex
operations on sched_lock earlier.
untimeout() not being called with Giant in those functions. For now,
use the sched_lock to protect the callout wheel in softclock() and in
the various timeout and callout functions.
Noticed by: tegge
type of software interrupt. Roughly, what used to be a bit in spending
now maps to a swi thread. Each thread can have multiple handlers, just
like a hardware interrupt thread.
- Instead of using a bitmask of pending interrupts, we schedule the specific
software interrupt thread to run, so spending, NSWI, and the shandlers
array are no longer needed. We can now have an arbitrary number of
software interrupt threads. When you register a software interrupt
thread via sinthand_add(), you get back a struct intrhand that you pass
to sched_swi() when you wish to schedule your swi thread to run.
- Convert the name of 'struct intrec' to 'struct intrhand' as it is a bit
more intuitive. Also, prefix all the members of struct intrhand with
'ih_'.
- Make swi_net() a MI function since there is now no point in it being
MD.
Submitted by: cp
- eliminate the fast/slow timeout lists for TCP and instead use a
callout entry for each timer.
- increase the TCP timer granularity to HZ
- implement "bad retransmit" recovery, as presented in
"On Estimating End-to-End Network Path Properties", by Allman and Paxson.
Submitted by: jlemon, wollmann
to manage their own memory. Tested on my machine (make buildworld).
I've made analogous changes on the alpha, but don't have a machine
to test.
Not-objected-to by: dg, gibbs
of time that the laptop was suspending. Thus, select() calls that might have
suspended rather than firing at 1hr + "time suspended" since the timer was
posted.
Adding:
options APM_FIXUP_CALLTODO
to the kernel config enables the patch.
[
This patch was slightly modified to use a consistant indent style and
I removed some unused local variables. After this has been tested a
few weeks we'll make the options the default, so for now I'm now
documenting it in LINT. Mike can later if he wants.
]
Reviewed by: Mike Smith <msmith@freebsd.org>
Submitted by: Ken Key <key@cs.utk.edu>
hash chain traversal isn't needed. This also allows untimeout to recompute
the hash to find the bucket that the entry to remove is stored in so
that each callout entry no longer needs to store that information.
Reviewed by: Nate Williams <nate@mt.sri.com>
Add support for "interrupt driven configuration hooks".
A component of the kernel can register a hook, most likely
during auto-configuration, and receive a callback once
interrupt services are available. This callback will occur before
the root and dump devices are configured, so the configuration
task can affect the selection of those two devices or complete
any tasks that need to be performed prior to launching init.
System boot is posponed so long as a hook is registered. The
hook owner is responsible for removing the hook once their task
is complete or the system boot can continue.
kern_acct.c kern_clock.c kern_exit.c kern_synch.c kern_time.c:
Change the interface and implementation for the kernel callout
service. The new implemntaion is based on the work of
Adam M. Costello and George Varghese, published in a technical
report entitled "Redesigning the BSD Callout and Timer Facilities".
The interface used in FreeBSD is a little different than the one
outlined in the paper. The new function prototypes are:
struct callout_handle timeout(void (*func)(void *),
void *arg, int ticks);
void untimeout(void (*func)(void *), void *arg,
struct callout_handle handle);
If a client wishes to remove a timeout, it must store the
callout_handle returned by timeout and pass it to untimeout.
The new implementation gives 0(1) insert and removal of callouts
making this interface scale well even for applications that
keep 100s of callouts outstanding.
See the updated timeout.9 man page for more details.
There are various options documented in i386/conf/LINT, there is more to
come over the next few days.
The kernel should run pretty much "as before" without the options to
activate SMP mode.
There are a handful of known "loose ends" that need to be fixed, but
have been put off since the SMP kernel is in a moderately good condition
at the moment.
This commit is the result of the tinkering and testing over the last 14
months by many people. A special thanks to Steve Passe for implementing
the APIC code!
form `tv = time'. Use a new function gettime(). The current version
just forces atomicicity without fixing precision or efficiency bugs.
Simplified some related valid accesses by using the central function.
changes, so don't expect to be able to run the kernel as-is (very well)
without the appropriate Lite/2 userland changes.
The system boots and can mount UFS filesystems.
Untested: ext2fs, msdosfs, NFS
Known problems: Incorrect Berkeley ID strings in some files.
Mount_std mounts will not work until the getfsent
library routine is changed.
Reviewed by: various people
Submitted by: Jeffery Hsu <hsu@freebsd.org>
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
I decided to do this for every hardclock() call instead of lazily
in microtime(). The lazy method is simpler but has more overhead
if microtime() is called a lot.
CPU_THISTICKLEN() is now a no-op and should probably go away.
Previously it did nothing directly but had the side effect of
setting i586_last_tick for CPU_CLOCKUPDATE() and i586_avg_tick for
debugging. CPU_CLOCKUPDATE() now uses a better method and
i586_avg_tick is too much trouble to maintain.
Reduced nesting of #includes in the usual case.
Increased nesting of #includes when CLOCK_HAIR is defined. This
is a kludge to get typedefs for inline functions only when the
inline functions are used. Normally only kern_clock.c defines
this. kern_clock.c can't include the i386 headers directly.
Removed unused LOCORE support.
Unstaticize a function in scsi/scsi_base that was used, with an undocumented
option.
My last count on the LINT kernel shows:
Total symbols: 3647
unref symbols: 463
undef symbols: 4
1 ref symbols: 1751
2 ref symbols: 485
Approaching the pain threshold now.
Move a lot of variables home to their own code (In good time before xmas :-)
Introduce the string descrition of format.
Add a couple more functions to poke into these marvels, while I try to
decide what the correct interface should look like.
Next is adding vars on the fly, and sysctl looking at them too.
Removed a tine bit of defunct and #ifdefed notused code in swapgeneric.
much as I'd like to, but the malloc stunt I tried for an interim for
sure does worse.
Now we can read and write from any kind of address-space, not only
user and kernel, using callbacks.
This may be over-generalization for now, but it's actually simpler.
Submitted by: terry (terry lambert)
This is a composite of 3 patch sets submitted by terry.
they are:
New low-level init code that supports loadbal modules better
some cleanups in the namei code to help terry in 16-bit character support
some changes to the mount-root code to make it a little more
modular..
NOTE: mounting root off cdrom or NFS MIGHT be broken as I haven't been able
to test those cases..
certainly mounting root of disk still works just fine..
mfs should work but is untested. (tomorrows task)
The low level init stuff includes a total rewrite of init_main.c
to make it possible for new modules to have an init phase by simply
adding an entry to a TEXT_SET (or is it DATA_SET) list. thus a new module can
be added to the kernel without editing any other files other than the
'files' file.
Improve hzto():
Round up instead of down and then add 1 tick. This fixes sleep(1)
sometimes sleeping for < 1 second and usleep(10000) sometimes sleeping
for as little as 1 usec + syscall time.
Don't do all the calculations at splhigh().
Don't depend on `tick' being a multiple of 1000.
Don't lose accuracy for `sec' between 0x7fffffff / 1000 - 1000 and
0x7fffffff / hz.
Don't assume that longs are 32 bits or that ints have the same size as
longs.
cycles. While waiting there I added a lot of the extra ()'s I have, (I have
never used LISP to any extent). So I compiled the kernel with -Wall and
shut up a lot of "suggest you add ()'s", removed a bunch of unused var's
and added a couple of declarations here and there. Having a lap-top is
highly recommended. My kernel still runs, yell at me if you kernel breaks.
This code is mostly taken from the 1.1 port (which was in turn taken from
Dave Mills's kern.tar.Z example). A few significant differences:
1) ntp_gettime() is now a MIB variable rather than a system call. A few
fiddles are done in libc to make it behave the same.
2) mono_time does not participate in the PLL adjustments.
3) A new interface has been defined (in <machine/clock.h>) for doing
possibly machine-dependent things around the time of the clock update.
This is used in Pentium kernels to disable interrupts, set `time', and
reset the CPU cycle counter as quickly as possible to avoid jitter in
microtime(). Measurements show an apparent resolution of a bit more than
8.14usec, which is reasonable given system-call overhead.
in your kernel config now).
2) Added ps ddb function from 1.1.5. Cleaned it up a bit and moved into its
own file.
3) Added \r handing in db_printf.
4) Added missing memory usage stats to statclock().
5) Added dummy function to pseudo_set so it will be emitted if there
are no other pseudo declarations.
- Delete redundant declarations.
- Add -Wredundant-declarations to Makefile.i386 so they don't come back.
- Delete sloppy COMMON-style declarations of uninitialized data in
header files.
- Add a few prototypes.
- Clean up warnings resulting from the above.
NB: ioconf.c will still generate a redundant-declaration warning, which
is unavoidable unless somebody volunteers to make `config' smarter.
