between creation of a file descriptor and close(2) when using kernel
assisted threads. What we do is stick descriptors in the table, but
mark them as "larval". This causes essentially everything to treat
it as a non-existent descriptor, except for fdalloc(), which sees a
filled slot so that it won't (incorrectly) allocate it again. When
a descriptor is fully constructed, the code that has constructed it
marks it as "mature" (which actually clears the "larval" flag), and
things continue to work as normal.
While here, gather all the code that gets a descriptor from the table
into a fd_getfile() function, and call it, rather than having the
same (sometimes incorrect) code copied all over the place.
fdexpand(). The former will return ENOSPC if there is not space
in the current filedesc table. The latter performs the expansion
of the filedesc table. This means that fdalloc() won't ever block,
and it gives callers an opportunity to clean up before the
potentially-blocking fdexpand() call.
Update all fdalloc() callers to deal with the need-to-fdexpand() case.
Rewrite unp_externalize() to use fdalloc() and fdexpand() in a
safe way, using an algorithm suggested by Bill Sommerfeld:
- Use a temporary array of integers to hold the new filedesc table
indexes. This allows us to repeat the loop if necessary.
- Loop through the array of file *'s, assigning them to filedesc table
slots. If fdalloc() indicates expansion is necessary, undo the
assignments we've done so far, expand, and retry the whole process.
- Once all file *'s have been assigned to slots, update the f_msgcount
and unp_rights counters.
- Right before we return, copy the temporary integer array to the message
buffer, and trim the length as before.
Note that once locking is added to the filedesc array, this entire
operation will be `atomic', in that the lock will be held while
file *'s are assigned to embryonic table slots, thus preventing anything
else from using them.
descriptor array, which may have blocked. Change callers of
fdalloc() to restart whatever they\'re doing if this condition
happens. (XXX unp_externalize() needs some work, but that will
be tackled later.)
Change finishdup() to close the descriptor in the `new\' slot if
one exists, and change sys_dup2() accordingly.
Closes a race condition when using kernel-assisted user threads.
While here, garbage-collect UF_MAPPED -- it is not used anywhere.
The ISO C standard says in 6.10.3.3 that if the result of using the
'##' operator "is not a valid preprocessing token, the behaviour is
undefined." Gcc 3.0 warns about this.
unions `union_elem: ...', and use c99 syntax `.union_elem = ...' only
where necessary.
in this case, there's no need to tag elf_probe_func because that's the
first union element, and therefore, the implicit case. only specifically
mention ecoff_probe_func where necessary.
if we decide to not use this c99 feature for now, at least there's now
less stuff to rip out.
Previously, we passed __FILE__ and __LINE__ on all pool_get/pool_set calls.
This change results in a measured 1.2% performance improvement in
ping-flood packets-per-second as reported by ping(8).
that the caller allocate the pool_item_header when it allocates the
pool page, so we can avoid a locking pitfall (sleeping with a simple
lock held).
Also revive pool_prime(), as there are some letigimate uses of it,
but in doing so, eliminate some of the bogosities of the old version
(i.e. don't do an implicit "setlowat", just prime the pool, and incr
the minpages for each additional page we add, and compute the number
of pages to prime in a way that callers would expect).
to 512. Apparently, there are ELF binaries with more than 128 section
headers - an example is one of Linux Word Perfect 8 utilities.
This fixes kern/12455 by Mark Davies.
flag.
EMUL_BSD_ASYNCIO_PIPE notes that the emulated binaries expect the original
BSD pipe behavior for asynchronous I/O, which is to fire SIGIO on read() and
write(). OSes without this flag do not expect any SIGIO to be fired on
read() and write() for pipes, even when async I/O was requested. As far as
we know, the OSes that need EMUL_BSD_ASYNCIO_PIPE are NetBSD, OSF/1 and
Darwin.
EMUL_BSD_ASYNCIO_PIPE notes that the emulated binaries expect the original
BSD pipe behavior for asynchronous I/O, which is to fire SIGIO on read() and
write(). OSes without this flag do not expect any SIGIO to be fired on
read() and write() for pipes, even when async I/O was requested. As far as
we know, the OSes that need EMUL_BSD_ASYNCIO_PIPE are NetBSD, OSF/1 and
Darwin.
EMUL_NO_SIGIO_ON_READ notes that the emulated binaries that requested
asynchrnous I/O expect the reader process to be notified by a SIGIO, but
not the writer process. OSes without this flag expect the reader and the
writer to be notified when some data has arrived or when some data have been
read. As far as we know, the OSes that need EMUL_NO_SIGIO_ON_READ are Linux
and SunOS.
thorpej