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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: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yuyang Du 2019-05-06 16:19:31 +08:00 committed by Ingo Molnar
parent 77a806922c
commit 154f185e9c
1 changed files with 10 additions and 11 deletions
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21
kernel/locking/lockdep.c
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@ -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;