From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>
Subject: [RFC v7 05/19] lockdep: Reduce the size of lock_list::distance
Date: Fri, 7 Aug 2020 15:42:24 +0800 [thread overview]
Message-ID: <20200807074238.1632519-6-boqun.feng@gmail.com> (raw)
In-Reply-To: <20200807074238.1632519-1-boqun.feng@gmail.com>
lock_list::distance is always not greater than MAX_LOCK_DEPTH (which
is 48 right now), so a u16 will fit. This patch reduces the size of
lock_list::distance to save space, so that we can introduce other fields
to help detect recursive read lock deadlocks without increasing the size
of lock_list structure.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
include/linux/lockdep.h | 2 +-
kernel/locking/lockdep.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 6b7cb390f19f..b85973515f84 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -212,7 +212,7 @@ struct lock_list {
struct lock_class *class;
struct lock_class *links_to;
const struct lock_trace *trace;
- int distance;
+ u16 distance;
/*
* The parent field is used to implement breadth-first search, and the
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2d9798b71f74..699e9039a9b3 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1320,7 +1320,7 @@ static struct lock_list *alloc_list_entry(void)
*/
static int add_lock_to_list(struct lock_class *this,
struct lock_class *links_to, struct list_head *head,
- unsigned long ip, int distance,
+ unsigned long ip, u16 distance,
const struct lock_trace *trace)
{
struct lock_list *entry;
@@ -2489,7 +2489,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next)
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next, int distance,
+ struct held_lock *next, u16 distance,
struct lock_trace **const trace)
{
struct lock_list *entry;
@@ -2622,7 +2622,7 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
goto out_bug;
for (;;) {
- int distance = curr->lockdep_depth - depth + 1;
+ u16 distance = curr->lockdep_depth - depth + 1;
hlock = curr->held_locks + depth - 1;
/*
--
2.28.0
next prev parent reply other threads:[~2020-08-07 7:43 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 7:42 [RFC v7 00/19] lockdep: Support deadlock detection for recursive read locks Boqun Feng
2020-08-07 7:42 ` [RFC v7 01/19] locking: More accurate annotations for read_lock() Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 02/19] lockdep/Documention: Recursive read lock detection reasoning Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 03/19] lockdep: Demagic the return value of BFS Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 04/19] lockdep: Make __bfs() visit every dependency until a match Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` Boqun Feng [this message]
2020-08-27 7:54 ` [tip: locking/core] lockdep: Reduce the size of lock_list::distance tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 06/19] lockdep: Introduce lock_list::dep Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 07/19] lockdep: Extend __bfs() to work with multiple types of dependencies Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 08/19] lockdep: Make __bfs(.match) return bool Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 09/19] lockdep: Support deadlock detection for recursive read locks in check_noncircular() Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 10/19] lockdep: Adjust check_redundant() for recursive read change Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 11/19] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-09-15 18:32 ` [RFC v7 11/19] " Qian Cai
2020-09-16 8:10 ` Boqun Feng
2020-09-16 16:14 ` Boqun Feng
2020-09-16 21:11 ` Qian Cai
2020-09-17 1:53 ` Boqun Feng
2020-08-07 7:42 ` [RFC v7 12/19] lockdep: Add recursive read locks into dependency graph Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-09-14 18:16 ` [RFC v7 12/19] " Qian Cai
2020-09-14 22:04 ` Qian Cai
2020-08-07 7:42 ` [RFC v7 13/19] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 14/19] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng
2020-08-21 17:41 ` Peter Zijlstra
2020-08-22 2:52 ` boqun.feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 15/19] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 16/19] lockdep/selftest: Add more recursive read related test cases Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 17/19] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 18/19] locking/selftest: Add test cases for queued_read_lock() Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07 7:42 ` [RFC v7 19/19] lockdep/selftest: Introduce recursion3 Boqun Feng
2020-08-27 7:54 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-21 19:56 ` [RFC v7 00/19] lockdep: Support deadlock detection for recursive read locks Peter Zijlstra
2020-08-23 1:12 ` boqun.feng
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