On Thu, Apr 07, 2005 at 12:43:02PM +0100, Christoph Hellwig wrote: > - switch all current semaphore users that don't need counting semaphores > over to use a mutex_t type. For now it can map to struct semaphore. > - rip out all existing complicated struct semaphore implementations and > replace it with a portable C implementation. There's not a lot of users > anyway. Add a mutex_t implementation that allows sensible assembly hooks > for architectures instead of reimplementing all of it > - add more features to mutex_t where nessecary
Oh dear, this is going to take a while. In any case, here is such a first step in creating such a sequence of patches. Located at http://www.kvack.org/~bcrl/patches/mutex-A0/ are the following patches: 00_mutex.diff - Introduces the basic mutex abstraction on top of the existing semaphore implementation. 01_i_sem.diff - Converts all users of i_sem to use the mutex abstraction. 10_new_mutex.diff - Replaces the semphore mutex with a new mutex derrived from Trond's iosem patch. Note that this fixes a serious bug in iosems: see the change in mutex_lock_wake_function that ignores the return value of default_wake_function, as on SMP a process might still be running while we actually made progress. sem-test.c - A basic stress tester for the mutex / semaphore. I'm still not convinced that introducing the mutex type is the best approach, especially given the history of the up()/down() implementation. On the aio side of things, I introduced the owner field in the mutex (as opposed to the flag in Trond's iosem) for the next patch in the series to enable something like the following api: int aio_lock_mutex(struct mutex *lock, struct iocb *iocb); ...generic_file_read.... { ret = mutex_lock_aio(&inode->i_sem, iocb); if (ret) return ret; /* aio_lock_mutex can return -EIOCBQUEUED */ ... mutex_unlock(&inode->i_sem); } mutex_lock_aio will attempt to take the lock if the iocb is not the owner, otherwise it returns immediately (ie ->owner == iocb). This will allow for code paths that support aio to follow a fairly similar coding style to the synchronous io path. More next week... -ben -- "Time is what keeps everything from happening all at once." -- John Wheeler - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
