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locking/lockdep: Reduce space occupied by stack traces

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Although commit 669de8bda8 ("kernel/workqueue: Use dynamic lockdep keys
for workqueues") unregisters dynamic lockdep keys when a workqueue is
destroyed, a side effect of that commit is that all stack traces
associated with the lockdep key are leaked when a workqueue is destroyed.
Fix this by storing each unique stack trace once. Other changes in this
patch are:

- Use NULL instead of { .nr_entries = 0 } to represent 'no trace'.
- Store a pointer to a stack trace in struct lock_class and struct
  lock_list instead of storing 'nr_entries' and 'offset'.

This patch avoids that the following program triggers the "BUG:
MAX_STACK_TRACE_ENTRIES too low!" complaint:

	#include <fcntl.h>
	#include <unistd.h>

	int main()
	{
		for (;;) {
			int fd = open("/dev/infiniband/rdma_cm", O_RDWR);
			close(fd);
		}
	}

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yuyang Du <duyuyang@gmail.com>
Link: https://lkml.kernel.org/r/20190722182443.216015-4-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Bart Van Assche 2019-07-22 11:24:42 -07:00 • committed by Ingo Molnar
parent a297042164
commit 12593b7467
3 changed files with 95 additions and 44 deletions
Download patch file Download diff file Expand all files Collapse all files

9
include/linux/lockdep.h
View file

@ -66,10 +66,7 @@ struct lock_class_key {
extern struct lock_class_key __lockdep_no_validate__;
struct lock_trace {
unsigned int nr_entries;
unsigned int offset;
};
struct lock_trace;
#define LOCKSTAT_POINTS 4
@ -105,7 +102,7 @@ struct lock_class {
* IRQ/softirq usage tracking bits:
*/
unsigned long usage_mask;
struct lock_trace usage_traces[XXX_LOCK_USAGE_STATES];
const struct lock_trace *usage_traces[XXX_LOCK_USAGE_STATES];
/*
* Generation counter, when doing certain classes of graph walking,
@ -193,7 +190,7 @@ struct lock_list {
struct list_head entry;
struct lock_class *class;
struct lock_class *links_to;
struct lock_trace trace;
const struct lock_trace *trace;
int distance;
/*