Async I/O OS specifities should now handled in OS specific code. Linux
has been done, but other emulation should be handled. See case LINUX_F_SETFL
in sys/compat/linux/common/linux_file.c:linux_sys_fcntl() for more details.
The data that has been collected yet:
Net Free Open Linux SunOS AIX OSF1 Darwin
send SIGIO to write end of pipe Y N N N N N Y Y
send SIGIO to read end of pipe Y Y N N N ? Y ?
send SIGIO to write end of socket Y Y Y N N Y Y Y
send SIGIO to read end of socket Y Y Y Y Y ? Y ?
neither it does send any SIGIO for pipes. If async I/O
was requested, we keep the SS_ASYNC in struct socket flag
set, but we clear SB_ASYNC flags on the sending buffer
(for socket), and on the sending and the receiving buffer
(for pipes).
Because we do not alter to SS_ASYNC in struct socket,
the Linux process keeps a consistent view of async I/O
status if it attemps to read the async flag (SS_ASYNC)
This async I/O problem does matters, since some Linux
a programs such as the JDK request async I/O on pipes,
but they fail if they happen to get a SIGIO to the write
end of the pipe.
struct socket so_state field to decide if we need to send asynchronous
notifications. This makes possible to request notification on write but
not on read, and vice versa.
This is used in Linux emulation code, because when async I/O is requested,
Linux does not send SIGIO to write end of sockets, and it never send any
SIGIO to any end of pipes. Il Linux emulation code, we then set SB_ASYNC
only on the read end of sockets, and on no end for pipes.
for FreeBSD project. Besides huge speed boost compared with socketpair-based
pipes, this implementation also uses pagable kernel memory instead of mbufs.
Significant differences to FreeBSD version:
* uses uvm_loan() facility for direct write
* async/SIGIO handling correct also for sync writer, async reader
* limits settable via sysctl, amountpipekva and nbigpipes available via sysctl
* pipes are unidirectional - this is enforced on file descriptor level
for now only, the code would be updated to take advantage of it
eventually
* uses lockmgr(9)-based locks instead of home brew variant
* scatter-gather write is handled correctly for direct write case, data
is transferred by PIPE_DIRECT_CHUNK bytes maximum, to avoid running out of kva
All FreeBSD/NetBSD specific code is within appropriate #ifdef, in preparation
to feed changes back to FreeBSD tree.
This pipe implementation is optional for now, add 'options NEW_PIPE'
to your kernel config to use it.
enabled by setting $rcshutdown_timeout to a number of seconds to wait for
before terminating rc.shutdown. This is disabled by default.
- Use symbolic names rather than numbers when defining a trap.
- Improve some comments.
on the dump device on sun3x. (sync with sun3)
Now savecore(8) can find core dump in dumpdev properly.
XXX "target kcore /dev/mem" on gdb does not work yet.
instead to store them. Add a macro to fetch the vaddr without them.
Make all variables/routines prefixed with pmap_
Cleanup & fix some of the vsid bitmap usage.
Cleanup DEBUG printfs. Add some more checks to pmap_pvo_to_pte.
MNT_NOSUID, just check MNT_NOSUID to clear the S{U,G}ID bits
in the attributes for the vnode we're about to exec.
We now check P_TRACED right before we would actually perform
the s{u,g}id function in the exec code.
This closes a race condition between exec of a setuid binary
and ptrace(2).
kleink