2007/4/26, Hans Petter Selasky <[EMAIL PROTECTED]>:
Hi,In the new USB stack I have defined the following: u_int32_t mtx_drop_recurse(struct mtx *mtx) { u_int32_t recurse_level = mtx->mtx_recurse; u_int32_t recurse_curr = recurse_level; mtx_assert(mtx, MA_OWNED); while(recurse_curr--) { mtx_unlock(mtx); } return recurse_level; } void mtx_pickup_recurse(struct mtx *mtx, u_int32_t recurse_level) { mtx_assert(mtx, MA_OWNED); while(recurse_level--) { mtx_lock(mtx); } return; } When I do a msleep() I do it like this: level = mtx_drop_recurse(ctd->p_mtx); error = msleep(ctd, ctd->p_mtx, 0, "config td sleep", timeout); mtx_pickup_recurse(ctd->p_mtx, level); Are there any comments on integrating this functionality into msleep(), and adding mtx_drop_recurse() and mtx_pickup_recurse() to the FreeBSD kernel?
Several times I thought to adding recursed mutex handling in msleep & condvar, but in the end the better approach is mantaining the current behaviour. Recursed mutexes often are results of incorrect locking strategies and catering that kind of errors is necessarily a bad idea. It is a lot better handling potential recursing mutexes outside from sleeping points (that is what your implementation does). Just, please, don't deal with internal struct mtx fields for that (so, please, don't refer to mtx->mtx_recurse) just use the mutex(9) API provided. Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
