From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Boqun Feng <boqun.feng@gmail.com>
Subject: [RFC tip/locking/lockdep v4 15/17] lockdep: Reduce the size of lock_list
Date: Tue, 9 Jan 2018 22:38:58 +0800 [thread overview]
Message-ID: <20180109143900.27475-16-boqun.feng@gmail.com> (raw)
In-Reply-To: <20180109143900.27475-1-boqun.feng@gmail.com>
We actually only need 4 bits for lock_list::dep and 1 bit for
lock_list::is_rr, besides lock_list::distance should always be no
greater than MAX_LOCKDEP_DEPTH(which is 48 right now), so a u16 will
fit, this patch then reduces the sizes of those fields to save space for
lock_list structure, as a result we can reduce the size increment
introduced by recursive read lock detection and keep the lock_list the
same size as before.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
include/linux/lockdep.h | 6 +++---
kernel/locking/lockdep.c | 11 ++++++-----
2 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 63b3504528d5..e43c77c125dd 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -186,11 +186,11 @@ struct lock_list {
struct list_head entry;
struct lock_class *class;
struct stack_trace trace;
- int distance;
+ u16 distance;
/* bitmap of different dependencies from head to this */
- u16 dep;
+ u8 dep;
/* used by BFS to record whether this is picked as a recursive read */
- u16 is_rr;
+ bool is_rr;
/*
* 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 d7cd98467243..4ca160517dcb 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -869,7 +869,7 @@ static struct lock_list *alloc_list_entry(void)
* Add a new dependency to the head of the list:
*/
static int add_lock_to_list(struct lock_class *this, struct list_head *head,
- unsigned long ip, int distance, unsigned int dep,
+ unsigned long ip, u16 distance, unsigned int dep,
struct stack_trace *trace)
{
struct lock_list *entry;
@@ -1058,7 +1058,7 @@ static inline unsigned int calc_dep(int prev, int next)
* N: non-recursive lock
* R: recursive read lock
*/
-static inline int pick_dep(u16 is_rr, u16 cap_dep)
+static inline int pick_dep(bool is_rr, u8 cap_dep)
{
if (is_rr) { /* could only pick -(N*)-> */
if (cap_dep & DEP_NN_MASK)
@@ -1143,7 +1143,8 @@ static enum bfs_result __bfs(struct lock_list *source_entry,
struct list_head *head;
struct circular_queue *cq = &lock_cq;
enum bfs_result ret = BFS_RNOMATCH;
- int is_rr, next_is_rr;
+ bool is_rr;
+ int next_is_rr;
if (match(source_entry, data)) {
*target_entry = source_entry;
@@ -1199,7 +1200,7 @@ static enum bfs_result __bfs(struct lock_list *source_entry,
next_is_rr = pick_dep(is_rr, entry->dep);
if (next_is_rr < 0)
continue;
- entry->is_rr = next_is_rr;
+ entry->is_rr = !!next_is_rr;
visit_lock_entry(entry, lock);
if (match(entry, data)) {
@@ -2148,7 +2149,7 @@ 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;
if (hlock->check) {
--
2.15.1
next prev parent reply other threads:[~2018-01-09 14:38 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-09 14:38 [RFC tip/locking/lockdep v4 00/17] lockdep: Support deadlock detection for recursive read locks Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 01/17] lockdep: Demagic the return value of BFS Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 02/17] lockdep: Make __bfs() visit every dependency until a match Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 03/17] lockdep: Redefine LOCK_*_STATE* bits Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 04/17] lockdep: Introduce lock_list::dep Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 05/17] lockdep: Extend __bfs() to work with multiple kinds of dependencies Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 06/17] lockdep: Support deadlock detection for recursive read in check_noncircular() Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 07/17] lockdep: Adjust check_redundant() for recursive read change Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 08/17] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 09/17] lockdep: Add recursive read locks into dependency graph Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 10/17] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 11/17] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 12/17] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 13/17] lockdep/selftest: Add more recursive read related test cases Boqun Feng
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 14/17] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng
2018-01-09 14:38 ` Boqun Feng [this message]
2018-01-09 14:38 ` [RFC tip/locking/lockdep v4 16/17] lockdep: Documention for recursive read lock detection reasoning Boqun Feng
2018-01-25 1:05 ` Randy Dunlap
2018-01-25 1:40 ` Boqun Feng
2018-01-09 14:39 ` [RFC tip/locking/lockdep v4 17/17] MAINTAINERS: Add myself as a LOCKING PRIMITIVES reviewer Boqun Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180109143900.27475-16-boqun.feng@gmail.com \
--to=boqun.feng@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).