From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH v5 6/7] locking/lockdep: Reuse freed chain_hlocks entries
Date: Tue, 4 Feb 2020 13:36:29 +0100 [thread overview]
Message-ID: <20200204123629.GO14914@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200203164147.17990-7-longman@redhat.com>
On Mon, Feb 03, 2020 at 11:41:46AM -0500, Waiman Long wrote:
> + if (unlikely(size < 2))
> + return; // XXX leak!
Stuck this on top...
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2631,7 +2631,8 @@ struct lock_chain lock_chains[MAX_LOCKDE
static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
unsigned long nr_zapped_lock_chains;
-unsigned int nr_free_chain_hlocks; /* Free cfhain_hlocks in buckets */
+unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
+unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
/*
@@ -2718,8 +2719,17 @@ static inline void add_chain_block(int o
int bucket = size_to_bucket(size);
int next = chain_block_buckets[bucket];
- if (unlikely(size < 2))
- return; // XXX leak!
+ if (unlikely(size < 2)) {
+ /*
+ * We can't store single entries on the freelist. Leak them.
+ *
+ * One possible way out would be to uniquely mark them, other
+ * than with CHAIN_BLK_FLAG, such that we can recover them when
+ * the block before it is re-added.
+ */
+ nr_lost_chain_hlocks++;
+ return;
+ }
init_chain_block(offset, next, bucket, size);
chain_block_buckets[bucket] = offset;
@@ -2798,8 +2808,8 @@ static int alloc_chain_hlocks(int req)
search:
/*
- * linear search in the 'dump' bucket; look for an exact match or the
- * largest block.
+ * linear search of the variable sized freelist; look for an exact
+ * match or the largest block.
*/
for_each_chain_block(0, prev, curr, next) {
size = chain_block_size(curr);
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -141,6 +141,7 @@ extern unsigned int nr_hardirq_chains;
extern unsigned int nr_softirq_chains;
extern unsigned int nr_process_chains;
extern unsigned int nr_free_chain_hlocks;
+extern unsigned int nr_lost_chain_hlocks;
extern unsigned int nr_large_chain_blocks;
extern unsigned int max_lockdep_depth;
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -278,9 +278,11 @@ static int lockdep_stats_show(struct seq
#ifdef CONFIG_PROVE_LOCKING
seq_printf(m, " dependency chains: %11lu [max: %lu]\n",
lock_chain_count(), MAX_LOCKDEP_CHAINS);
- seq_printf(m, " dependency chain hlocks: %11lu [max: %lu]\n",
- MAX_LOCKDEP_CHAIN_HLOCKS - nr_free_chain_hlocks,
+ seq_printf(m, " dependency chain hlocks used: %11lu [max: %lu]\n",
+ MAX_LOCKDEP_CHAIN_HLOCKS - (nr_free_chain_hlocks - nr_lost_chain_hlocks),
MAX_LOCKDEP_CHAIN_HLOCKS);
+ seq_printf(m, " dependency chain hlocks free: %11lu\n", nr_free_chain_hlocks);
+ seq_printf(m, " dependency chain hlocks lost: %11lu\n", nr_lost_chain_hlocks);
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
next prev parent reply other threads:[~2020-02-04 12:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-03 16:41 [PATCH v5 0/7] locking/lockdep: Reuse zapped " Waiman Long
2020-02-03 16:41 ` [PATCH v5 1/7] locking/lockdep: Decrement irq context counters when removing lock chain Waiman Long
2020-02-03 16:41 ` [PATCH v5 2/7] locking/lockdep: Display irq_context names in /proc/lockdep_chains Waiman Long
2020-02-03 16:41 ` [PATCH v5 3/7] locking/lockdep: Track number of zapped classes Waiman Long
2020-02-03 16:41 ` [PATCH v5 4/7] locking/lockdep: Throw away all lock chains with zapped class Waiman Long
2020-02-03 16:41 ` [PATCH v5 5/7] locking/lockdep: Track number of zapped lock chains Waiman Long
2020-02-03 16:41 ` [PATCH v5 6/7] locking/lockdep: Reuse freed chain_hlocks entries Waiman Long
2020-02-04 12:36 ` Peter Zijlstra [this message]
2020-02-04 14:54 ` Waiman Long
2020-02-04 16:45 ` Waiman Long
2020-02-05 9:41 ` Peter Zijlstra
2020-02-05 13:59 ` Waiman Long
2020-02-04 15:42 ` Peter Zijlstra
2020-02-04 16:12 ` Waiman Long
2020-02-04 16:26 ` Waiman Long
2020-02-04 16:57 ` Waiman Long
2020-02-05 9:48 ` Peter Zijlstra
2020-02-05 14:03 ` Waiman Long
2020-02-03 16:41 ` [PATCH v5 7/7] locking/lockdep: Add a fast path for chain_hlocks allocation Waiman Long
2020-02-04 12:47 ` Peter Zijlstra
2020-02-04 15:07 ` Waiman Long
2020-02-04 13:18 ` Peter Zijlstra
2020-02-04 13:44 ` Peter Zijlstra
2020-02-04 18:02 ` Waiman Long
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