From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751870AbdBBVFf (ORCPT ); Thu, 2 Feb 2017 16:05:35 -0500 Received: from mail03-md.ns.itscom.net ([175.177.155.113]:52069 "EHLO mail03-md.ns.itscom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751206AbdBBVFe (ORCPT ); Thu, 2 Feb 2017 16:05:34 -0500 From: "J. R. Okajima" Subject: Re: [PATCH 3/3] lockdep: new annotation lock_downgrade() To: Peter Zijlstra Cc: kbuild test robot , kbuild-all@01.org, linux-kernel@vger.kernel.org In-Reply-To: <20170202184540.GZ6515@twins.programming.kicks-ass.net> References: <1486053497-9948-3-git-send-email-hooanon05g@gmail.com> <201702030137.ONyfgEno%fengguang.wu@intel.com> <20170202184540.GZ6515@twins.programming.kicks-ass.net> Date: Fri, 03 Feb 2017 06:05:31 +0900 Message-ID: <2978.1486069531@jrobl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra: > > >> kernel/locking/rwsem.c:126:2: error: implicit declaration of functi= on 'lock_downgrade' [-Werror=3Dimplicit-function-declaration] > > lock_downgrade(&sem->dep_map, _RET_IP_); > > ^~~~~~~~~~~~~~ ::: > This is what you need !LOCKDEP stubs for ;-) Ok, here is the update. Just one line added. J. R. Okajima commit 6874cbfb3c4f757efecbeb800bfd4db1050698f6 Author: J. R. Okajima Date: Thu Feb 2 23:41:38 2017 +0900 lockdep: new annotation lock_downgrade() = The commit f831948 2016-11-30 locking/lockdep: Provide a type check for lock_is_= held didn't fully support rwsem. Here downgrade_write() supports the added = type. = Originally-written-by: Peter Zijlstra See-also: http://marc.info/?l=3Dlinux-kernel&m=3D148581164003149&w=3D2 Signed-off-by: J. R. Okajima diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 0345cbf..ba75d06 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -361,6 +361,8 @@ static inline void lock_set_subclass(struct lockdep_ma= p *lock, lock_set_class(lock, lock->name, lock->key, subclass, ip); } = +extern void lock_downgrade(struct lockdep_map *lock, unsigned long ip); + extern void lockdep_set_current_reclaim_state(gfp_t gfp_mask); extern void lockdep_clear_current_reclaim_state(void); extern void lockdep_trace_alloc(gfp_t mask); @@ -413,6 +415,7 @@ static inline void lockdep_on(void) = # define lock_acquire(l, s, t, r, c, n, i) do { } while (0) # define lock_release(l, n, i) do { } while (0) +# define lock_downgrade(l, i) do { } while (0) # define lock_set_class(l, n, k, s, i) do { } while (0) # define lock_set_subclass(l, s, i) do { } while (0) # define lockdep_set_current_reclaim_state(g) do { } while (0) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 7dc8f8e..6a4a740 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3523,6 +3523,44 @@ __lock_set_class(struct lockdep_map *lock, const ch= ar *name, return 1; } = +static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr =3D current; + struct held_lock *hlock; + unsigned int depth; + int i; + + depth =3D curr->lockdep_depth; + /* + * This function is about (re)setting the class of a held lock, + * yet we're not actually holding any locks. Naughty user! + */ + if (DEBUG_LOCKS_WARN_ON(!depth)) + return 0; + + hlock =3D find_held_lock(curr, lock, depth, &i); + if (!hlock) + return print_unlock_imbalance_bug(curr, lock, ip); + + curr->lockdep_depth =3D i; + curr->curr_chain_key =3D hlock->prev_chain_key; + + WARN(hlock->read, "downgrading a read lock"); + hlock->read =3D 1; + hlock->acquire_ip =3D ip; + + if (validate_held_lock(curr, depth, i)) + return 0; + + /* + * I took it apart and put it back together again, except now I have + * these 'spare' parts.. where shall I put them. + */ + if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth !=3D depth)) + return 0; + return 1; +} + /* * Remove the lock to the list of currently held locks - this gets * called on mutex_unlock()/spin_unlock*() (or on a failed @@ -3749,6 +3787,23 @@ void lock_set_class(struct lockdep_map *lock, const= char *name, } EXPORT_SYMBOL_GPL(lock_set_class); = +void lock_downgrade(struct lockdep_map *lock, unsigned long ip) +{ + unsigned long flags; + + if (unlikely(current->lockdep_recursion)) + return; + + raw_local_irq_save(flags); + current->lockdep_recursion =3D 1; + check_flags(flags); + if (__lock_downgrade(lock, ip)) + check_chain_key(current); + current->lockdep_recursion =3D 0; + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_downgrade); + /* * We are not always called with irqs disabled - do that here, * and also avoid lockdep recursion: diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 45ba475..31db3ef 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -123,10 +123,8 @@ EXPORT_SYMBOL(up_write); */ void downgrade_write(struct rw_semaphore *sem) { - /* - * lockdep: a downgraded write will live on as a write - * dependency. - */ + lock_downgrade(&sem->dep_map, _RET_IP_); + rwsem_set_reader_owned(sem); __downgrade_write(sem); }