To do this, initialize the d_maj member of the cdevsw to MAJOR_AUTO.
When the cdevsw is first passed to make_dev() a free major number
will be assigned.
Until we have a bit more experience with this a printf will announce
this fact.
Major numbers are not reclaimed, so loading/unloading the same
device driver which uses MAJOR_AUTO will eventually deplete the
pool of free major numbers and the system will panic when it can
not allocate one. Still undecided who to invonvenience with the
solution to this.
td_wmesg field in the thread structure points to the description string of
the condition variable or mutex. If the condvar or the mutex had been
initialized from a loadable module that was unloaded in the meantime,
td_wmesg may now point to invalid memory. Retrieving the process table now
may panic the kernel (or access junk). Setting the td_wmesg field to NULL
after unblocking on the condvar/mutex prevents this panic.
PR: kern/47408
Approved by: jake (mentor)
turns runs its tasks free of Giant too. It is intended that as drivers
become locked down, they will move out of the old, Giant-bound taskqueue
and into this new one. The old taskqueue has been renamed to
taskqueue_swi_giant, and the new one keeps the name taskqueue_swi.
delta 1.371) we must ensure that we do not get ourselves into a
recursive trap endlessly trying to clean up after ourselves.
Reported by: Attila Nagy <bra@fsn.hu>
Sponsored by: DARPA & NAI Labs.
o Always check for null when dereferencing the filename component.
o Implement a try-and-backoff method for allocating memory to
dump stats to avoid a spin-lock -> sleep-lock mutex lock order
panic with WITNESS.
Approved by: des, markm (mentor)
Not objected: jhb
track of the number of dirty buffers held by a vnode. When a
bdwrite is done on a buffer, check the existing number of dirty
buffers associated with its vnode. If the number rises above
vfs.dirtybufthresh (currently 90% of vfs.hidirtybuffers), one
of the other (hopefully older) dirty buffers associated with
the vnode is written (using bawrite). In the event that this
approach fails to curb the growth in it the vnode's number of
dirty buffers (due to soft updates rollback dependencies),
the more drastic approach of doing a VOP_FSYNC on the vnode
is used. This code primarily affects very large and actively
written files such as snapshots. This change should eliminate
hanging when taking snapshots or doing background fsck on
very large filesystems.
Hopefully, one day it will be possible to cache filesystem
metadata in the VM cache as is done with file data. As it
stands, only the buffer cache can be used which limits total
metadata storage to about 20Mb no matter how much memory is
available on the system. This rather small memory gets badly
thrashed causing a lot of extra I/O. For example, taking a
snapshot of a 1Tb filesystem minimally requires about 35,000
write operations, but because of the cache thrashing (we only
have about 350 buffers at our disposal) ends up doing about
237,540 I/O's thus taking twenty-five minutes instead of four
if it could run entirely in the cache.
Reported by: Attila Nagy <bra@fsn.hu>
Sponsored by: DARPA & NAI Labs.
- Remove the buftimelock mutex and acquire the buf's interlock to protect
these fields instead.
- Hold the vnode interlock while locking bufs on the clean/dirty queues.
This reduces some cases from one BUF_LOCK with a LK_NOWAIT and another
BUF_LOCK with a LK_TIMEFAIL to a single lock.
Reviewed by: arch, mckusick
- Get rid of the useless atop() / pmap_phys_address() detour. The
device mmap handlers must now give back the physical address
without atop()'ing it.
- Don't borrow the physical address of the mapping in the returned
int. Now we properly pass a vm_offset_t * and expect it to be
filled by the mmap handler when the mapping was successful. The
mmap handler must now return 0 when successful, any other value
is considered as an error. Previously, returning -1 was the only
way to fail. This change thus accidentally fixes some devices
which were bogusly returning errno constants which would have been
considered as addresses by the device pager.
- Garbage collect the poorly named pmap_phys_address() now that it's
no longer used.
- Convert all the d_mmap_t consumers to the new API.
I'm still not sure wheter we need a __FreeBSD_version bump for this,
since and we didn't guarantee API/ABI stability until 5.1-RELEASE.
Discussed with: alc, phk, jake
Reviewed by: peter
Compile-tested on: LINT (i386), GENERIC (alpha and sparc64)
Runtime-tested on: i386
in massive locking issues on diskless systems.
It is also not clear that this sysctl is non-dangerous in its
requirements for locked down memory on large RAM systems.
Retire the "d_dump_t" and use the "dumper_t" type instead.
Dumper_t takes a void * as first arg which is more general than the
dev_t taken by d_dump_t. (Remember: we could have net-dumpers if
somebody wrote us one!)
Define the convention for GEOM controlled disk devices to be that the
first argument to the dumper function is the struct disk pointer.
Change device drivers accordingly.
dev_t to the method functions.
The dev_t can still be found at struct consdev *->cn_dev.
Add a void *cn_arg element to struct consdev which the drivers can use
for retrieving their softc.
In devsw() return dead_cdevsw instead of NULL in case the dev_t does not
have a si_devsw.
This may improve our survival chances with devices which go away unexpectedly.
compile-time constants). That is, a "bucket" now is not necessarily
a page-worth of mbufs or clusters, but it is MBUF_BUCK_SZ, CLUS_BUCK_SZ
worth of mbufs, clusters.
o Rename {mbuf,clust}_limit to {mbuf,clust}_hiwm and introduce
{mbuf,clust}_lowm, which currently has no effect but will be used
to set the low watermarks.
o Fix netstat so that it can deal with the differently-sized buckets
and teach it about the low watermarks too.
o Make sure the per-cpu stats for an absent CPU has mb_active set to 0,
explicitly.
o Get rid of the allocate refcounts from mbuf map mess. Instead,
just malloc() the refcounts in one shot from mbuf_init()
o Clean up / update comments in subr_mbuf.c
used to share resource limits between rfork threads, but never was.
Removing it makes resource limit locking much simpler -- only the current
process can change the contents of the structure that p_limit points to.
reference counter array for mbuf clusters. I don't know
how this got past early testing nor how it survived so long
without getting caught. If anyone was seeing really really
bizarre memory corruption in a few mbufs this would be why.
