Commit 75dd602a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

lockdep: Fix lock_chain::base size

lock_chain::base is used to store an index into the chain_hlocks[]
array, however that array contains more elements than can be indexed
using the u16.

Change the lock_chain structure to use a bitfield to encode the data
it needs and add BUILD_BUG_ON() assertions to check the fields are
wide enough.

Also, for DEBUG_LOCKDEP, assert that we don't run out of elements of
that array; as that would wreck the collision detectoring.
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160330093659.GS3408@twins.programming.kicks-ass.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c2469756
...@@ -196,9 +196,11 @@ struct lock_list { ...@@ -196,9 +196,11 @@ struct lock_list {
* We record lock dependency chains, so that we can cache them: * We record lock dependency chains, so that we can cache them:
*/ */
struct lock_chain { struct lock_chain {
u8 irq_context; /* see BUILD_BUG_ON()s in lookup_chain_cache() */
u8 depth; unsigned int irq_context : 2,
u16 base; depth : 6,
base : 24;
/* 4 byte hole */
struct hlist_node entry; struct hlist_node entry;
u64 chain_key; u64 chain_key;
}; };
......
...@@ -2176,15 +2176,37 @@ static inline int lookup_chain_cache(struct task_struct *curr, ...@@ -2176,15 +2176,37 @@ static inline int lookup_chain_cache(struct task_struct *curr,
chain->irq_context = hlock->irq_context; chain->irq_context = hlock->irq_context;
i = get_first_held_lock(curr, hlock); i = get_first_held_lock(curr, hlock);
chain->depth = curr->lockdep_depth + 1 - i; chain->depth = curr->lockdep_depth + 1 - i;
BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) { if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
chain->base = nr_chain_hlocks; chain->base = nr_chain_hlocks;
nr_chain_hlocks += chain->depth;
for (j = 0; j < chain->depth - 1; j++, i++) { for (j = 0; j < chain->depth - 1; j++, i++) {
int lock_id = curr->held_locks[i].class_idx - 1; int lock_id = curr->held_locks[i].class_idx - 1;
chain_hlocks[chain->base + j] = lock_id; chain_hlocks[chain->base + j] = lock_id;
} }
chain_hlocks[chain->base + j] = class - lock_classes; chain_hlocks[chain->base + j] = class - lock_classes;
} }
if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
nr_chain_hlocks += chain->depth;
#ifdef CONFIG_DEBUG_LOCKDEP
/*
* Important for check_no_collision().
*/
if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
if (debug_locks_off_graph_unlock())
return 0;
print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
dump_stack();
return 0;
}
#endif
hlist_add_head_rcu(&chain->entry, hash_head); hlist_add_head_rcu(&chain->entry, hash_head);
debug_atomic_inc(chain_lookup_misses); debug_atomic_inc(chain_lookup_misses);
inc_chains(); inc_chains();
......
...@@ -141,6 +141,8 @@ static int lc_show(struct seq_file *m, void *v) ...@@ -141,6 +141,8 @@ static int lc_show(struct seq_file *m, void *v)
int i; int i;
if (v == SEQ_START_TOKEN) { if (v == SEQ_START_TOKEN) {
if (nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)
seq_printf(m, "(buggered) ");
seq_printf(m, "all lock chains:\n"); seq_printf(m, "all lock chains:\n");
return 0; return 0;
} }
......
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