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 14:40:18 +0100 [thread overview]
Message-ID: <20170228134018.GK5680@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:
> + /*
> + * If the previous in held_locks can create a proper dependency
> + * with a target crosslock, then we can skip commiting this,
> + * since "the target crosslock -> the previous lock" and
> + * "the previous lock -> this lock" can cover the case. So we
> + * keep the previous's gen_id to make the decision.
> + */
> + unsigned int prev_gen_id;
> +static void add_xhlock(struct held_lock *hlock, unsigned int prev_gen_id)
> +{
> + struct hist_lock *xhlock;
> +
> + xhlock = alloc_xhlock();
> +
> + /* Initialize hist_lock's members */
> + xhlock->hlock = *hlock;
> + xhlock->nmi = !!(preempt_count() & NMI_MASK);
> + /*
> + * prev_gen_id is used to skip adding dependency at commit step,
> + * when the previous lock in held_locks can do that instead.
> + */
> + xhlock->prev_gen_id = prev_gen_id;
> + xhlock->work_id = current->work_id;
> +
> + xhlock->trace.nr_entries = 0;
> + xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES;
> + xhlock->trace.entries = xhlock->trace_entries;
> + xhlock->trace.skip = 3;
> + save_stack_trace(&xhlock->trace);
> +}
> +static void check_add_xhlock(struct held_lock *hlock)
> +{
> + struct held_lock *prev;
> + struct held_lock *start;
> + unsigned int gen_id;
> + unsigned int gen_id_invalid;
> +
> + if (!current->xhlocks || !depend_before(hlock))
> + return;
> +
> + gen_id = (unsigned int)atomic_read(&cross_gen_id);
> + /*
> + * gen_id_invalid must be too old to be valid. That means
> + * current hlock should not be skipped but should be
> + * considered at commit step.
> + */
> + gen_id_invalid = gen_id - (UINT_MAX / 4);
> + start = current->held_locks;
> +
> + for (prev = hlock - 1; prev >= start &&
> + !depend_before(prev); prev--);
> +
> + if (prev < start)
> + add_xhlock(hlock, gen_id_invalid);
> + else if (prev->gen_id != gen_id)
> + add_xhlock(hlock, prev->gen_id);
> +}
> +static int commit_xhlocks(struct cross_lock *xlock)
> +{
> + struct task_struct *curr = current;
> + struct hist_lock *xhlock_c = xhlock_curr(curr);
> + struct hist_lock *xhlock = xhlock_c;
> +
> + do {
> + xhlock = xhlock_prev(curr, xhlock);
> +
> + if (!xhlock_used(xhlock))
> + break;
> +
> + if (before(xhlock->hlock.gen_id, xlock->hlock.gen_id))
> + break;
> +
> + if (same_context_xhlock(xhlock) &&
> + before(xhlock->prev_gen_id, xlock->hlock.gen_id) &&
> + !commit_xhlock(xlock, xhlock))
> + return 0;
> + } while (xhlock_c != xhlock);
> +
> + return 1;
> +}
So I'm still struggling with prev_gen_id; is it an optimization or is it
required for correctness?
--
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next prev parent reply other threads:[~2017-02-28 13:40 UTC|newest]
Thread overview: 62+ 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 [this message]
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
2017-03-05 3:08 ` Byungchul Park
2017-03-07 11:42 ` Peter Zijlstra
2017-03-03 0:39 ` Byungchul Park
2017-02-28 15:49 ` Peter Zijlstra
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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