Lock of struct filedesc, file, pgrp, session and sigio is now ready
for testing.
The patch is at
http://people.FreeBSD.org/~tanimura/patches/fd_pgrp.diff.gz
Below is the brief description of locking.
1. struct filedesc and struct file
- fd_mtx protects struct filedesc.
- f_mtx protects struct file. Refer to sys/file.h for detail.
- Do not look up a file descriptor table directly but use FFIND*
macros defined in sys/filedesc.h. They handle locking a file
descriptor table and a file descriptor.
- getvnode() locks a file descriptor.
- p_fd may change during the life of a process if it is sharing its
file descriptor table when the process calls execve(2). As nobody
except curproc and the parent process in fork1() touches the file
descriptor table of a process, the lock type of p_fd should be "(a)
only touched by curproc or parent during fork/wait."
2. struct proc, struct pgrp and struct session
- pgrphash_lock and pg_mtx protects struct pgrp. Refer to sys/proc.h
for detail.
- s_mtx protects struct session. Refer to sys/proc.h for detail.
- Introduce p_pgrpmtx to protect p_pgrp of struct proc in cooperation
with p_mtx. This allows locking of a process in a process group
without lock order reversal. The lock order of them is shown below.
1st: p_pgrpmtx
2st: pg_mtx
3rd: p_mtx
- You may lock more than one process groups provided that they belong
to an identical session and you lock the session in advance.
- psignal() requires the lock of the process group to which a
destination process belongs if the property of a signal includes
SA_STOP. PROC_LOCK_PSIGNAL() and PROC_UNLOCK_PSIGNAL() handle
those lock and unlock.
TODO: Pass a signal to PROC_(UN)LOCK_PSIGNAL() to avoid unnecessary
lock.
- pgsignal() requires the lock of a destination process group.
3. struct sigio
- struct sigio forms a list(struct sigiolst), residing in a process or
a process group. p_mtx of a process or pg_mtx of a process group is
responsible to lock struct sigiolst. The members of struct sigio
other than sio_pgsigio never change.
- A macro FUNSETOWN locks the list of struct sigio, calls funsetown()
and unlocks the list.
--
Seigo Tanimura <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
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