From: Peter Zijlstra <peterz@infradead.org>
To: Byungchul Park <byungchul.park@lge.com>
Cc: mingo@kernel.org, tglx@linutronix.de, walken@google.com,
boqun.feng@gmail.com, kirill@shutemov.name,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
npiggin@gmail.com
Subject: Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature
Date: Tue, 28 Feb 2017 16:49:00 +0100 [thread overview]
Message-ID: <20170228154900.GL5680@worktop> (raw)
In-Reply-To: <1484745459-2055-7-git-send-email-byungchul.park@lge.com>
On Wed, Jan 18, 2017 at 10:17:32PM +0900, Byungchul Park wrote:
> +struct cross_lock {
> + /*
> + * When more than one acquisition of crosslocks are overlapped,
> + * we do actual commit only when ref == 0.
> + */
> + atomic_t ref;
That comment doesn't seem right, should that be: ref != 0 ?
Also; would it not be much clearer to call this: nr_blocked, or waiters
or something along those lines, because that is what it appears to be.
> + /*
> + * Seperate hlock instance. This will be used at commit step.
> + *
> + * TODO: Use a smaller data structure containing only necessary
> + * data. However, we should make lockdep code able to handle the
> + * smaller one first.
> + */
> + struct held_lock hlock;
> +};
> +static int add_xlock(struct held_lock *hlock)
> +{
> + struct cross_lock *xlock;
> + unsigned int gen_id;
> +
> + if (!depend_after(hlock))
> + return 1;
> +
> + if (!graph_lock())
> + return 0;
> +
> + xlock = &((struct lockdep_map_cross *)hlock->instance)->xlock;
> +
> + /*
> + * When acquisitions for a xlock are overlapped, we use
> + * a reference counter to handle it.
Handle what!? That comment is near empty.
> + */
> + if (atomic_inc_return(&xlock->ref) > 1)
> + goto unlock;
So you set the xlock's generation only once, to the oldest blocking-on
relation, which makes sense, you want to be able to related to all
historical locks since.
> +
> + gen_id = (unsigned int)atomic_inc_return(&cross_gen_id);
> + xlock->hlock = *hlock;
> + xlock->hlock.gen_id = gen_id;
> +unlock:
> + graph_unlock();
> + return 1;
> +}
> +void lock_commit_crosslock(struct lockdep_map *lock)
> +{
> + struct cross_lock *xlock;
> + unsigned long flags;
> +
> + if (!current->xhlocks)
> + return;
> +
> + if (unlikely(current->lockdep_recursion))
> + return;
> +
> + raw_local_irq_save(flags);
> + check_flags(flags);
> + current->lockdep_recursion = 1;
> +
> + if (unlikely(!debug_locks))
> + return;
> +
> + if (!graph_lock())
> + return;
> +
> + xlock = &((struct lockdep_map_cross *)lock)->xlock;
> + if (atomic_read(&xlock->ref) > 0 && !commit_xhlocks(xlock))
You terminate with graph_lock() held.
Also, I think you can do the atomic_read() outside of graph lock, to
avoid taking graph_lock when its 0.
> + return;
> +
> + graph_unlock();
> + current->lockdep_recursion = 0;
> + raw_local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL_GPL(lock_commit_crosslock);
> +
> +/*
> + * return 0: Need to do normal release operation.
> + * return 1: Done. No more release ops is needed.
> + */
> +static int lock_release_crosslock(struct lockdep_map *lock)
> +{
> + if (cross_lock(lock)) {
> + atomic_dec(&((struct lockdep_map_cross *)lock)->xlock.ref);
> + return 1;
> + }
> + return 0;
> +}
> +
> +static void cross_init(struct lockdep_map *lock, int cross)
> +{
> + if (cross)
> + atomic_set(&((struct lockdep_map_cross *)lock)->xlock.ref, 0);
> +
> + lock->cross = cross;
> +}
next prev parent reply other threads:[~2017-02-28 15:50 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-18 13:17 [PATCH v5 00/13] lockdep: Implement crossrelease feature Byungchul Park
2017-01-18 13:17 ` [PATCH v5 01/13] lockdep: Refactor lookup_chain_cache() Byungchul Park
2017-01-19 9:16 ` Boqun Feng
2017-01-19 9:52 ` Byungchul Park
2017-01-26 7:53 ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 02/13] lockdep: Fix wrong condition to print bug msgs for MAX_LOCKDEP_CHAIN_HLOCKS Byungchul Park
2017-01-18 13:17 ` [PATCH v5 03/13] lockdep: Add a function building a chain between two classes Byungchul Park
2017-01-18 13:17 ` [PATCH v5 04/13] lockdep: Refactor save_trace() Byungchul Park
2017-01-18 13:17 ` [PATCH v5 05/13] lockdep: Pass a callback arg to check_prev_add() to handle stack_trace Byungchul Park
2017-01-26 7:43 ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 06/13] lockdep: Implement crossrelease feature Byungchul Park
2017-02-28 12:26 ` Peter Zijlstra
2017-02-28 12:45 ` Peter Zijlstra
2017-02-28 12:49 ` Peter Zijlstra
2017-03-01 6:20 ` Byungchul Park
2017-02-28 13:05 ` Peter Zijlstra
2017-02-28 13:28 ` Byungchul Park
2017-02-28 13:35 ` Peter Zijlstra
2017-02-28 14:00 ` Byungchul Park
2017-02-28 13:10 ` Peter Zijlstra
2017-02-28 13:24 ` Byungchul Park
2017-02-28 18:29 ` Peter Zijlstra
2017-03-01 4:40 ` Byungchul Park
2017-03-01 10:45 ` Peter Zijlstra
2017-03-01 12:10 ` Byungchul Park
2017-02-28 13:40 ` Peter Zijlstra
2017-03-01 5:43 ` Byungchul Park
2017-03-01 12:28 ` Peter Zijlstra
2017-03-02 13:40 ` Peter Zijlstra
2017-03-03 0:17 ` Byungchul Park
2017-03-03 8:14 ` Peter Zijlstra
2017-03-03 9:13 ` Peter Zijlstra
2017-03-03 9:32 ` Peter Zijlstra
2017-03-05 3:33 ` Byungchul Park
2017-08-10 12:18 ` [tip:locking/core] locking/lockdep: Avoid creating redundant links tip-bot for Peter Zijlstra
2017-03-05 3:08 ` [PATCH v5 06/13] lockdep: Implement crossrelease feature Byungchul Park
2017-03-07 11:42 ` Peter Zijlstra
2017-03-03 0:39 ` Byungchul Park
2017-02-28 15:49 ` Peter Zijlstra [this message]
2017-03-01 5:17 ` Byungchul Park
2017-03-01 6:18 ` Byungchul Park
2017-03-02 2:52 ` Byungchul Park
2017-02-28 18:15 ` Peter Zijlstra
2017-03-01 7:21 ` Byungchul Park
2017-03-01 10:43 ` Peter Zijlstra
2017-03-01 12:27 ` Byungchul Park
2017-03-02 4:20 ` Matthew Wilcox
2017-03-02 4:45 ` byungchul.park
2017-03-02 14:39 ` Matthew Wilcox
2017-03-02 23:50 ` Byungchul Park
2017-03-05 8:01 ` Byungchul Park
2017-03-14 7:36 ` Byungchul Park
2017-03-02 13:41 ` Peter Zijlstra
2017-03-02 23:43 ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 07/13] lockdep: Make print_circular_bug() aware of crossrelease Byungchul Park
2017-01-18 13:17 ` [PATCH v5 08/13] lockdep: Apply crossrelease to completions Byungchul Park
2017-01-18 13:17 ` [PATCH v5 09/13] pagemap.h: Remove trailing white space Byungchul Park
2017-01-18 13:17 ` [PATCH v5 10/13] lockdep: Apply crossrelease to PG_locked locks Byungchul Park
2017-01-18 13:17 ` [PATCH v5 11/13] lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked Byungchul Park
2017-01-18 13:17 ` [PATCH v5 12/13] lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext Byungchul Park
2017-01-18 13:17 ` [PATCH v5 13/13] lockdep: Crossrelease feature documentation Byungchul Park
2017-01-20 9:08 ` [REVISED DOCUMENT] " Byungchul Park
2017-02-20 8:38 ` [PATCH v5 00/13] lockdep: Implement crossrelease feature Byungchul Park
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