Merge branch 'ipc-scalability'
Merge IPC cleanup and scalability patches from Andrew Morton.
This cleans up many of the oddities in the IPC code, uses the list
iterator helpers, splits out locking and adds per-semaphore locks for
greater scalability of the IPC semaphore code.
Most normal user-level locking by now uses futexes (ie pthreads, but
also a lot of specialized locks), but SysV IPC semaphores are apparently
still used in some big applications, either for portability reasons, or
because they offer tracking and undo (and you don't need to have a
special shared memory area for them).
Our IPC semaphore scalability was pitiful. We used to lock much too big
ranges, and we used to have a single ipc lock per ipc semaphore array.
Most loads never cared, but some do. There are some numbers in the
individual commits.
* ipc-scalability:
ipc: sysv shared memory limited to 8TiB
ipc/msg.c: use list_for_each_entry_[safe] for list traversing
ipc,sem: fine grained locking for semtimedop
ipc,sem: have only one list in struct sem_queue
ipc,sem: open code and rename sem_lock
ipc,sem: do not hold ipc lock more than necessary
ipc: introduce lockless pre_down ipcctl
ipc: introduce obtaining a lockless ipc object
ipc: remove bogus lock comment for ipc_checkid
ipc/msgutil.c: use linux/uaccess.h
ipc: refactor msg list search into separate function
ipc: simplify msg list search
ipc: implement MSG_COPY as a new receive mode
ipc: remove msg handling from queue scan
ipc: set EFAULT as default error in load_msg()
ipc: tighten msg copy loops
ipc: separate msg allocation from userspace copy
ipc: clamp with min()
