KTRFAC_DROP to track instances when ktrace events are dropped due to the
request pool being exhausted. When a thread tries to post a ktrace event
and is unable to due to no available ktrace request objects, it sets
KTRFAC_DROP in its process' p_traceflag field. The next trace event to
successfully post from that process will set the KTR_DROP flag in the
header of the request going out and clear KTRFAC_DROP.
The KTR_DROP flag is the high bit in the type field of the ktr_header
structure. Older kdump binaries will simply complain about an unknown type
when seeing an entry with KTR_DROP set. Note that KTR_DROP being set on a
record in a ktrace file does not tell you anything except that at least one
event from this process was dropped prior to this event. The user has no
way of knowing what types of events were dropped nor how many were dropped.
Requested by: phk
struct proc as p_tracecred alongside the current cache of the vnode in
p_tracep. This credential is then used for all later ktrace operations on
this file rather than using the credential of the current thread at the
time of each ktrace event.
- Now that we have multiple ktrace-related items in struct proc that are
pointers, rename p_tracep to p_tracevp to make it less ambiguous.
Requested by: rwatson (1)
- Create a new function bdone() which sets B_DONE and calls wakup(bp). This
is suitable for use as b_iodone for buf consumers who are not going
through the buf cache.
- Create a new function bwait() which waits for the buf to be done at a set
priority and with a specific wmesg.
- Replace several cases where the above functionality was implemented
without locking with the new functions.
possible for some time.
- Lock the buf before accessing fields. This should very rarely be locked.
- Assert that B_DELWRI is set after we acquire the buf. This should always
be the case now.
requiring locked bufs in vfs_bio_awrite(). Previously the buf could
have been written out by fsync before we acquired the buf lock if it
weren't for giant. The cluster_wbuild() handles this race properly but
the single write at the end of vfs_bio_awrite() would not.
- Modify flushbufqueues() so there is only one copy of the loop. Pass a
parameter in that says whether or not we should sync bufs with deps.
- Call flushbufqueues() a second time and then break if we couldn't find
any bufs without deps.
than a MAXPHYS size block ahead. Having this set too high just leaves
other processes starved for IO and screws up interactive response. Let the
users with RAID set it higher when they need it.
- If SYSCTL_OUT() fails in sysctl_kern_proc_args(), return the error
instead of ignoring it if we have new arguments for the process.
- If the new arguments for a process are too long, return ENOMEM instead of
returning success but not doing the actual copy.
Submitted by: bde
hold hold it across the check to avoid extra lock operations in the
common case.
- Copy in the new args to a temporary pargs structure before we drop the
reference to the old one. Thus, if the copyin() fails, the process
arguments are unchanged rather than being deleted. Also, p_args is no
longer NULL during the sysctl operation.
it from its pgrp to avoid leaving zombies around with p_pgrp == NULL.
This bug was apparent as a NULL-dereference in the pid selection code
in fork1().
closely what function is really doing. Update all existing consumers
to use the new name.
Introduce a new vfs_stdsync function, which iterates over mount
point's vnodes and call FSYNC on each one of them in turn.
Make nwfs and smbfs use this new function instead of rolling their
own identical sync implementations.
Reviewed by: jeff
a parameter instead of using the level of a given witness. When
recursing, pass an indent level of indent + 1.
- Make use of the information witness_levelall() provides in
witness_display_list() to use an O(n) algorithm instead of an O(n^2)
algo to decide which witnesses to display hierarchies from. Basically,
we only display a hierarchy for witnesses with a level of 0.
- Add a new per-witness flag that is reset at the start of
witness_display() for all witness's and is set the first time a witness
is displayed in witness_displaydescendants(). If a witness is
encountered more than once in the lock order tree (which happens often),
witness_displaydescendants() marks the later occurrences with the string
"(already displayed)" and doesn't display the subtree under that
witness. This avoids duplicating large amounts of the lock order tree
in the 'show witness' output in DDB.
All these changes serve to make 'show witness' a lot more readable and
useful than it was previously.
adds a witness to the child list of a parent witness. rebalancetree()
runs through the entire tree removing direct descendants of witnesses
who already have said child witness as an indirect descendant through
another direct descendant. itismychild() now calls insertchild()
followed by rebalancetree() and no longer needs the evil hack of
having static recursed variable.
- Add a function reparentchildren() that adds all the direct descendants
of one witness as direct descendants of another witness.
- Change the return value of itismychild() and similar functions so that
they return 0 in the case of failure due to lack of resources instead
of 1. This makes the return value more intuitive.
- Check the return value of itismychild() when defining the static lock
order in witness_initialize().
- Don't try to setup a lock instance in witness_lock() if itismychild()
fails. Witness is hosed anyways so no need to do any more witness
related activity at that point. It also makes the code flow easier to
understand.
- Add a new depart() function as the opposite of enroll(). When the
reference count of a witness drops to 0 in witness_destroy(), this
function is called on that witness. First, it runs through the
lock order tree using reparentchildren() to reparent direct descendants
of the departing witness to each of the witness' parents in the tree.
Next, it releases it's own child list and other associated resources.
Finally it calls rebalanacetree() to rebalance the lock order tree.
- Sort function prototypes into something closer to alphabetical order.
As a result of these changes, there should no longer be 'dead' witnesses
in the order tree, and repeatedly loading and unloading a module should no
longer exhaust witness of its internal resources.
Inspired by: gallatin
recursing on a lock instead of before. This fixes a bug where WITNESS
could get a little confused if you did an sx_tryslock() on a sx lock that
you already had an slock on. WITNESS would still function correctly but
it could result in weirdness in the output of 'show locks'. This also
makes it possible for mtx_trylock() to recurse on a lock.
used popped into my head during my morning commute a few weeks ago, but
it is also very similar (though a bit simpler) to a patch that mini@
developed a while ago. Basically, each eventhandler list has a mutex and
a run count. During an eventhandler invocation, the mutex is held while
we traverse the list but is dropped while we execute actual handlers. Also,
a runcount counter is incremented at the start of an invocation and
decremented at the end of an invocation. Adding to the list is not a big
deal since the reference of a thread currently executing the handlers
remains valid across an add operation. Whether or not new handlers are
executed by threads currently executing the handlers for a given list is
indeterminate however. The harder case is when a handler is removed from
the list. If the runcount is zero, the handler is simply removed from the
list directly. If the runcount is not zero, then another thread is
currently executing the handlers of this list, so the priority of this
handler is set to a magic value (currently -1) to mark it as dead. Dead
handlers are not executed during an invocation. If the runcount is zero
after it is decremented at the end of an invocation, then a new
eventhandler_prune_list() function is called to remove dead handlers from
the list.
Additional minor notes:
- All the common parts of EVENTHANDLER_INVOKE() and
EVENTHANDLER_FAST_INVOKE() have been merged into a common
_EVENTHANDLER_INVOKE() macro to reduce duplication and ease maintenance.
- KTR logging for eventhandlers is now available via the KTR_EVH mask.
- The global eventhander_mutex is no longer recursive.
Tested by: scottl (SMP i386)
- Issue the io that we will later block on prior to doing cluster read ahead
so that it is more likely to be ready when we block.
- Loop issuing clustered reads until we've exhausted the seq count supplied
by the file system.
- Use a sysctl tunable "vfs.read_max" to determine the maximum number of
blocks that we'll read ahead.
I had commented the #ifdef INVARIANTS checks out to make sure I ran this
code in all kernels and forgot to comment the #ifdefs back in before I
committed.
Spotted by: bmilekic
[1] PHCC = Pointy Hat Correction Commit
ddb 'show locks' command. Thus, move witness_list() to the #ifdef DDB
section and remove extra checks for calling this function outside of
DDB. Also, witness_list() now returns void instead of returning an int.
Reported by: Steve Ames <steve@energistic.com>
Prodded by: davidxu
Remove an incorrect comment. (Incrementing an object's reference count
does not prevent a process from exiting. The real concern here is that the
physical page must not be deleted until transmission is complete. That is
already handled by the VM system and sf_buf_free().)
Tested by: ken
is more robust and prevents the hijacking of /dev/console for the typical
mistake.
Remove unneeded MAJOR_AUTO uses, it is only needed explicitly now if the
driver source has cross-branch compatibility to old releases.
the device statistics structures into userland instead of using sysctl.
Introduce new devstat_new_entry() function which allocates the devstat
structure an calls devstat_add_entry() on it.
- On receive, vm_map_lookup() needs to trigger the creation of a shadow
object. To make that happen, call vm_map_lookup() with PROT_WRITE
instead of PROT_READ in vm_pgmoveco().
- On send, a shadow object will be created by the vm_map_lookup() in
vm_fault(), but vm_page_cowfault() will delete the original page from
the backing object rather than simply letting the legacy COW mechanism
take over. In other words, the new page should be added to the shadow
object rather than replacing the old page in the backing object. (i.e.
vm_page_cowfault() should not be called in this case.) We accomplish
this by making sure fs.object == fs.first_object before calling
vm_page_cowfault() in vm_fault().
Submitted by: gallatin, alc
Tested by: ken
witness. Sleepable locks such as sx locks always come before all mutexes
including Giant. However, the static lock order list placed Giant before
the proctree and allproc sx locks. This resulted in witness creating a
cycle in its lock order "tree" (real trees don't have cycles) leading to
infinite recursion and eventually a double fault. To fix, put Giant after
sx locks in the lock order list.
