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Date: Mon, 13 Jul 2009 16:02:05 +0800
From: Dave Young <hidave.darkstar@...il.com>
To: tom.leiming@...il.com
Cc: a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org,
akpm@...ux-foundation.org, mingo@...e.hu
Subject: Re: [RESEND PATCH 04/11] kernel:lockdep:implement
check_noncircular() by BFS
On Sun, Jun 28, 2009 at 11:04:39PM +0800, tom.leiming@...il.com wrote:
> From: Ming Lei <tom.leiming@...il.com>
>
> This patch uses BFS to implement check_noncircular() and
> prints the generated shortest circle if exists.
>
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
> kernel/lockdep.c | 89 ++++++++++++++++++++++-------------------------------
> 1 files changed, 37 insertions(+), 52 deletions(-)
>
> diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> index ce6d09e..f740088 100644
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -985,12 +985,7 @@ static inline int __bfs_backward(struct lock_list *src_entry,
> * Recursive, forwards-direction lock-dependency checking, used for
> * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
> * checking.
> - *
> - * (to keep the stackframe of the recursive functions small we
> - * use these global variables, and we also mark various helper
> - * functions as noinline.)
> */
> -static struct held_lock *check_source, *check_target;
>
> /*
> * Print a dependency chain entry (this is only done when a deadlock
> @@ -1014,7 +1009,9 @@ print_circular_bug_entry(struct lock_list *target, unsigned int depth)
> * header first:
> */
> static noinline int
> -print_circular_bug_header(struct lock_list *entry, unsigned int depth)
> +print_circular_bug_header(struct lock_list *entry, unsigned int depth,
> + struct held_lock *check_src,
> + struct held_lock *check_tgt)
> {
> struct task_struct *curr = current;
>
> @@ -1027,9 +1024,9 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
> printk( "-------------------------------------------------------\n");
> printk("%s/%d is trying to acquire lock:\n",
> curr->comm, task_pid_nr(curr));
> - print_lock(check_source);
> + print_lock(check_src);
> printk("\nbut task is already holding lock:\n");
> - print_lock(check_target);
> + print_lock(check_tgt);
> printk("\nwhich lock already depends on the new lock.\n\n");
> printk("\nthe existing dependency chain (in reverse order) is:\n");
>
> @@ -1043,36 +1040,24 @@ static inline int class_equal(struct lock_list *entry, void *data)
> return entry->class == data;
> }
>
> -static noinline int print_circular_bug(void)
> +static noinline int print_circular_bug(struct lock_list *this,
Shouldn't be 'static noinline int' here? Same question to following ones.
> + struct lock_list *target,
> + struct held_lock *check_src,
> + struct held_lock *check_tgt)
> {
> struct task_struct *curr = current;
> - struct lock_list this;
> - struct lock_list *target;
> struct lock_list *parent;
> - int result;
> unsigned long depth;
>
> if (!debug_locks_off_graph_unlock() || debug_locks_silent)
> return 0;
>
> - this.class = hlock_class(check_source);
> - this.parent = NULL;
> - if (!save_trace(&this.trace))
> + if (!save_trace(&this->trace))
> return 0;
>
> - result = __bfs_forward(&this,
> - hlock_class(check_target),
> - class_equal,
> - &target);
> - if (result) {
> - printk("\n%s:search shortest path failed:%d\n", __func__,
> - result);
> - return 0;
> - }
> -
> depth = get_lock_depth(target);
>
> - print_circular_bug_header(target, depth);
> + print_circular_bug_header(target, depth, check_src, check_tgt);
>
> parent = get_lock_parent(target);
>
> @@ -1090,6 +1075,16 @@ static noinline int print_circular_bug(void)
> return 0;
> }
>
> +static int noinline print_bfs_bug(int ret)
> +{
> + if (!debug_locks_off_graph_unlock())
> + return 0;
> +
> + WARN(1, "lockdep bfs error:%d\n", ret);
> +
> + return 0;
> +}
> +
> #define RECURSION_LIMIT 40
>
> static int noinline print_infinite_recursion_bug(void)
> @@ -1168,31 +1163,17 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
> * lead to <target>. Print an error and return 0 if it does.
> */
> static noinline int
> -check_noncircular(struct lock_class *source, unsigned int depth)
> +check_noncircular(struct lock_list *root, struct lock_class *target,
> + struct lock_list **target_entry)
> {
> - struct lock_list *entry;
> + int result;
>
> - if (lockdep_dependency_visit(source, depth))
> - return 1;
> + debug_atomic_inc(&nr_cyclic_checks);
>
> - debug_atomic_inc(&nr_cyclic_check_recursions);
> - if (depth > max_recursion_depth)
> - max_recursion_depth = depth;
> - if (depth >= RECURSION_LIMIT)
> - return print_infinite_recursion_bug();
> - /*
> - * Check this lock's dependency list:
> - */
> - list_for_each_entry(entry, &source->locks_after, entry) {
> - if (entry->class == hlock_class(check_target))
> - return 2;
> - debug_atomic_inc(&nr_cyclic_checks);
> - if (check_noncircular(entry->class, depth+1) == 2)
> - return 2;
> - }
> - return 1;
> -}
> + result = __bfs_forward(root, target, class_equal, target_entry);
>
> + return result;
> +}
>
> #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
> /*
> @@ -1586,6 +1567,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
> {
> struct lock_list *entry;
> int ret;
> + struct lock_list this;
> + struct lock_list *uninitialized_var(target_entry);
>
> /*
> * Prove that the new <prev> -> <next> dependency would not
> @@ -1596,11 +1579,13 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
> * We are using global variables to control the recursion, to
> * keep the stackframe size of the recursive functions low:
> */
> - check_source = next;
> - check_target = prev;
> -
> - if (check_noncircular(hlock_class(next), 0) == 2)
> - return print_circular_bug();
> + this.class = hlock_class(next);
> + this.parent = NULL;
> + ret = check_noncircular(&this, hlock_class(prev), &target_entry);
> + if (unlikely(!ret))
> + return print_circular_bug(&this, target_entry, next, prev);
> + else if (unlikely(ret < 0))
> + return print_bfs_bug(ret);
>
> if (!check_prev_add_irq(curr, prev, next))
> return 0;
> --
> 1.6.0.GIT
>
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