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Commit 154f185e authored by Yuyang Du's avatar Yuyang Du Committed by Ingo Molnar
Browse files

locking/lockdep: Update comments on dependency search 



The breadth-first search is implemented as flat-out non-recursive now, but
the comments are still describing it as recursive, update the comments in
that regard.

Signed-off-by: default avatarYuyang Du <duyuyang@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-16-duyuyang@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 77a80692

kernel/locking/lockdep.c

+10 −11
Original line number Diff line number Diff line
@@ -1381,6 +1381,10 @@ static inline struct list_head *get_dep_list(struct lock_list *lock, int offset) 
	return lock_class + offset;

}



/*

 * Forward- or backward-dependency search, used for both circular dependency

 * checking and hardirq-unsafe/softirq-unsafe checking.

 */

static int __bfs(struct lock_list *source_entry,

		 void *data,

		 int (*match)(struct lock_list *entry, void *data),
@@ -1461,12 +1465,6 @@ static inline int __bfs_backwards(struct lock_list *src_entry, 


}



/*

 * Recursive, forwards-direction lock-dependency checking, used for

 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe

 * checking.

 */



static void print_lock_trace(struct lock_trace *trace, unsigned int spaces)

{

	unsigned long *entries = stack_trace + trace->offset;
@@ -2285,7 +2283,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, int read) 


/*

 * There was a chain-cache miss, and we are about to add a new dependency

 * to a previous lock. We recursively validate the following rules:

 * to a previous lock. We validate the following rules:

 *

 *  - would the adding of the <prev> -> <next> dependency create a

 *    circular dependency in the graph? [== circular deadlock]
@@ -2335,11 +2333,12 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, 
	/*

	 * Prove that the new <prev> -> <next> dependency would not

	 * create a circular dependency in the graph. (We do this by

	 * forward-recursing into the graph starting at <next>, and

	 * checking whether we can reach <prev>.)

	 * a breadth-first search into the graph starting at <next>,

	 * and check whether we can reach <prev>.)

	 *

	 * We are using global variables to control the recursion, to

	 * keep the stackframe size of the recursive functions low:

	 * The search is limited by the size of the circular queue (i.e.,

	 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes

	 * in the graph whose neighbours are to be checked.

	 */

	this.class = hlock_class(next);

	this.parent = NULL;