that the events queue is empty. In other case we're able to hit the race
where for example da0s1 is tasted by some other class, which means that
da0 is open with exclusive bit set, which means that we can't open da0
for writing if it is our component.
Reported by: Attila Nagy <bra@fsn.hu> (and somebody else sometime ago,
but I cannot find who it was)
transfer timeouts that typically cause a transfer to be completed
twice, resulting in panics and page faults:
o A transfer completion interrupt could arrive while an abort_task
event was set up, so the transfer would be aborted after it had
completed. This is very easy to reproduce. Fix this by setting
the transfer status to USBD_TIMEOUT before scheduling the
abort_task so that the transfer completion code will ignore it.
o The transfer completion code could execute concurrently with the
timeout callout, leaving the callout blocked (e.g. waiting for
Giant) while the transfer completion code runs. In this case,
callout_stop() does not prevent the callout from running, so
again the timeout code would run after the transfer was complete.
Handle this case by checking the return value from callout_stop(),
and ignoring the transfer if the callout could not be removed.
o Finally, protect against a timeout callout occurring while a
transfer is being aborted by another process. Here we arrange
for the timeout processing to ignore the transfer, and use
callout_drain() to ensure that the callout has really gone before
completing the transfer.
This was tested by repeatedly performing USB transfers with a timeout
set to approximately the same as the normal transfer completion
time. In the PR below, apparently this occurred by accident with a
particular printer and the default timeout.
PR: kern/71491
changes associated with adding System V IPC support. This will prevent
old modules from being used with the new kernel, and new modules from
being used with the old kernel.
appropriate for different tag requirements. With the former global pool,
bounce pages might get allocated that are appropriate for one tag, but not
appropriate for another, but the system had no way to distinguish between them.
Now zones with distinct attributes are created to hold pages, and each tag
that requires bouncing is associated with a zone. New zones are created as
needed if no existing zones can meet the requirements of the tag. Stats for
each zone are tracked via the hw.busdma sysctl node.
This should help drivers that are failing with mysterious data corruption.
MFC After: 1 week
includes the latter, but also declares variables which are defined
in kern/subr_param.c).
Change som VM parameters from quad_t to unsigned long. They refer to
quantities (size limits for text, heap and stack segments) which must
necessarily be smaller than the size of the address space, so long is
adequate on all platforms.
MFC after: 1 week
sensitive, but less excercised location (the watchdog). While here use the
*_start_locked function directly to avoid drop, grab, drop lock.
I have to be very careful with future ALTQ patches!
Found & reviewed by: rwatson
MFC after: 3 days
The tunable vfs.devfs.fops controls this feature and defaults to off.
When enabled (vfs.devfs.fops=1 in loader), device vnodes opened
through a filedescriptor gets a special fops vector which instead
of the detour through the vnode layer goes directly to DEVFS.
Amongst other things this allows us to run Giant free read/write to
device drivers which have been weaned off D_NEEDGIANT.
Currently this means /dev/null, /dev/zero, disks, (and maybe the
random stuff ?)
On a 700MHz K7 machine this doubles the speed of
dd if=/dev/zero of=/dev/null bs=1 count=1000000
This roughly translates to shaving 2usec of each read/write syscall.
The poll/kqfilter paths need more work before they are giant free,
this work is ongoing in p4::phk_bufwork
Please test this and report any problems, LORs etc.
