implementation is by no means perfect as far as some of the algorithms
that it uses and the fact that it is missing some functionality (try
locks and upgrades/downgrades are not there yet), however it does seem
to work in my local testing. There is more detail in the comments in the
code, but the short version follows.
A reader/writer lock is very much like a regular mutex: it cannot be held
across a voluntary sleep; it can be acquired in an interrupt thread; if
the lock is held by a writer then the priority of any threads that block
on the lock will be lent to the owner; the simple case lock operations all
are done in a single atomic op. It also shares some similiarities
with sx locks: it supports reader/writer semantics (multiple readers,
but single writers); readers are allowed to recurse, but writers are not.
We can extend this implementation further by either improving algorithms
or adding new functionality, but this should at least give us a base to
work with now.
Reviewed by: arch (in theory)
Tested on: i386 (4 cpu box with a kernel module that used 4 threads
that randomly chose between read locks and write locks
that ran w/o panicing for over a day solid. It usually
panic'd within a few seconds when there were bugs during
testing. :) The kernel module source is available on
request.)
queues in turnstiles. Add a new thread member td_tsqueue which contains
the sub-queue of a turnstile that a thread is on when it is blocked on a
turnstile.
each turnstile. Also, allow for the owner thread pointer of a turnstile
to be NULL. This is needed for the upcoming reader/writer lock
implementation.
- Add a new ddb command 'show turnstile' that will look up the turnstile
associated with the given lock argument and display useful information
like the list of threads blocked on each queue, etc. If there isn't an
active turnstile for a lock at the specified address, then the function
will see if there is an active turnstile at the specified address and
display info about it if so.
- Adjust the mutex code to handle the turnstile API changes.
Tested on: i386 (all), alpha, amd64, sparc64 (1 and 3)
argument and looks for a sleep queue associated with that wait channel.
If it finds one it will display information such as the list of threads
sleeping on that queue. If it can't find a sleep queue for that wait
channel, then it will see if that address matches any of the active
sleep queues. If so, it will display information about the sleepq at the
specified address.
is a fatal fault if we are holding any non-sleepable locks. This should
cut down on the number of bogus LORs we currently get when the kernel
panics due to a NULL (or bogus) pointer dereference that goes wandering
off into the VM system which tries to acquire locks and then kicks off
the spurious LORs. This should probably be ported to all the archs at
some point.
Tested on: i386
The difference between WITNESS_CHECK() and WITNESS_WARN() is that
WITNESS_CHECK() should be used in the places that the return value of
witness_warn() is checked, whereas WITNESS_WARN() should be used in places
where the return value is ignored. Specifically, in a kernel without
WITNESS enabled, WITNESS_WARN() evaluates to an empty string where as
WITNESS_CHECK evaluates to 0. I also updated the one place that was
checking the return value of WITNESS_WARN() to use WITNESS_CHECK.
sysctl then it will clear the KTR buffer. Note that if you have active
KTR traces at the same time as a clear operation the behavior is undefined,
though it shouldn't panic.
they are. They should be NULL at this point, except if we're coming from
swapdev_strategy().
It should only affect the case where we're swapping directly on a file over
NFS.
For example, you can dynamically generate and load configuration file
depending on the hardware configuration with the following template:
mediaSetCDROM
mediaOpen
command='/dist/rescue/sh /dist/scripts/install.sh'
system
mediaClose
configFile=/tmp/generated.cfg
loadConfig
Now we have full access to files on the media before installation begins.
into the card's memory.
# this eliminates a more of the ifdef soup in if_ed and if_edvar
# I've fixed the cbus drivers, but can't test them all easily.
If I've broken anything, please let me know.
by NGM_PPPOE_SETMODE message. When D-Link compat mode is on, we will
broadcast PADI with empty Service-Name to all listening hooks.
o Rewrite the compatibility options. Before we had two modes - standard
and non-standard (aka 3Com). Now we have standard mode and two compat
flags, that can be combined.
o Be consistent and do s/STUPID/3COM/g. I don't say that 3Com mode isn't
stupid, just want to make code easier to read.
to properly configure the right interface to use.
Also call the mediachg function when we set flags UP and are already
running. If this were a pure ifmedia driver, we'd not need to do this
since we'd be ignoring the linkX flags.
This reduces the number of ifdefs to support sub-devices a little as a
nice side effect. It also reduces the number of hpp interfaces
exposed by 33%.
man page that the ifconfig option link2 is used to disable the AUI
transceiver on the 3com boards (should also say HP PC Lan+). This
makes the connection clearer.
Add a note about why we set this flag prior to attaching the device.
We never set or clear the flag later, only test it. There can be no
races here, but this might be asthetically displeasing to some. Also
note that we may no longer need to have this knob at all as we may be
able to do it with the more sophisticated rc.d scripts we have today I
think the only reason it is there is because we didn't used to allow
its proper setting when configured to get the IP address via DHCP.
I'll note that this would be better handled by using ifmedia for all
ed cards, not just those with a miibus...
This is important with MegaLib, when issuing a GET_REBUILD_PROG since
it returns an error if the drive is not in rebuild state.
This will be MFC'ed shortly.
Submitted by: ps
Reviewed by: scottl
Found by: ambrisko
