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Commit 311d82ce authored by Patrick Daly's avatar Patrick Daly
Browse files

dma-buf: Add reference count leak tracing 



CONFIG_DEBUG_DMA_BUF_REF will collect stacktraces for
each call to dma_buf_get and dma_buf_put to help identify
leaks.

Change-Id: If299d73fbde80fc41d2a2150c4b6b8e7223734fa
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent ceb432de

drivers/dma-buf/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -30,4 +30,15 @@ config SW_SYNC 
	  WARNING: improper use of this can result in deadlocking kernel

	  drivers from userspace. Intended for test and debug only.



config DEBUG_DMA_BUF_REF

	bool "DEBUG Reference Count"

	depends on STACKDEPOT

	depends on DMA_SHARED_BUFFER

	default n

	---help---

	  Save stack traces for every call to dma_buf_get and dma_buf_put, to

	  help debug memory leaks. Potential leaks may be found by manually

	  matching the get/put call stacks.  This feature consumes extra memory

	  in order to save the stack traces using STACKDEPOT.



endmenu

drivers/dma-buf/Makefile

+1 −0
Original line number Diff line number Diff line 
obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o

obj-$(CONFIG_SYNC_FILE)		+= sync_file.o

obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o

obj-$(CONFIG_DEBUG_DMA_BUF_REF)	+= dma-buf-ref.o

drivers/dma-buf/dma-buf-ref.c

0 → 100644
+123 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2018, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and

 * only version 2 as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 */



#include <linux/dma-buf.h>

#include <linux/slab.h>

#include <linux/stackdepot.h>

#include <linux/stacktrace.h>

#include <linux/seq_file.h>



#define DMA_BUF_STACK_DEPTH (16)



struct dma_buf_ref {

	struct list_head list;

	depot_stack_handle_t handle;

	int count;

};



void dma_buf_ref_init(struct dma_buf *dmabuf)

{

	INIT_LIST_HEAD(&dmabuf->refs);

}



void dma_buf_ref_destroy(struct dma_buf *dmabuf)

{

	struct dma_buf_ref *r, *n;



	mutex_lock(&dmabuf->lock);

	list_for_each_entry_safe(r, n, &dmabuf->refs, list) {

		list_del(&r->list);

		kfree(r);

	}

	mutex_unlock(&dmabuf->lock);

}



static void dma_buf_ref_insert_handle(struct dma_buf *dmabuf,

				      depot_stack_handle_t handle,

				      int count)

{

	struct dma_buf_ref *r;



	mutex_lock(&dmabuf->lock);

	list_for_each_entry(r, &dmabuf->refs, list) {

		if (r->handle == handle) {

			r->count += count;

			goto out;

		}

	}



	r = kzalloc(sizeof(*r), GFP_KERNEL);

	if (!r)

		goto out;



	INIT_LIST_HEAD(&r->list);

	r->handle = handle;

	r->count = count;

	list_add(&r->list, &dmabuf->refs);



out:

	mutex_unlock(&dmabuf->lock);

}



void dma_buf_ref_mod(struct dma_buf *dmabuf, int nr)

{

	unsigned long entries[DMA_BUF_STACK_DEPTH];

	struct stack_trace trace = {

		.nr_entries = 0,

		.entries = entries,

		.max_entries = DMA_BUF_STACK_DEPTH,

		.skip = 1

	};

	depot_stack_handle_t handle;



	save_stack_trace(&trace);

	if (trace.nr_entries != 0 &&

	    trace.entries[trace.nr_entries-1] == ULONG_MAX)

		trace.nr_entries--;



	handle = depot_save_stack(&trace, GFP_KERNEL);

	if (!handle)

		return;



	dma_buf_ref_insert_handle(dmabuf, handle, nr);

}



/**

 * Called with dmabuf->lock held

 */

int dma_buf_ref_show(struct seq_file *s, struct dma_buf *dmabuf)

{

	char *buf;

	struct dma_buf_ref *ref;

	int count = 0;

	struct stack_trace trace;



	buf = (void *)__get_free_page(GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	list_for_each_entry(ref, &dmabuf->refs, list) {

		count += ref->count;



		seq_printf(s, "References: %d\n", ref->count);

		depot_fetch_stack(ref->handle, &trace);

		snprint_stack_trace(buf, PAGE_SIZE, &trace, 0);

		seq_puts(s, buf);

		seq_putc(s, '\n');

	}



	seq_printf(s, "Total references: %d\n\n\n", count);

	free_page((unsigned long)buf);



	return 0;

}

drivers/dma-buf/dma-buf.c

+9 −0
Original line number Diff line number Diff line
@@ -93,6 +93,8 @@ static int dma_buf_release(struct inode *inode, struct file *file) 
	list_del(&dmabuf->list_node);

	mutex_unlock(&db_list.lock);



	dma_buf_ref_destroy(dmabuf);



	if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])

		reservation_object_fini(dmabuf->resv);
@@ -495,6 +497,9 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) 
	mutex_init(&dmabuf->lock);

	INIT_LIST_HEAD(&dmabuf->attachments);



	dma_buf_ref_init(dmabuf);

	dma_buf_ref_mod(dmabuf, 1);



	mutex_lock(&db_list.lock);

	list_add(&dmabuf->list_node, &db_list.head);

	mutex_unlock(&db_list.lock);
@@ -556,6 +561,7 @@ struct dma_buf *dma_buf_get(int fd) 
		fput(file);

		return ERR_PTR(-EINVAL);

	}

	dma_buf_ref_mod(file->private_data, 1);



	return file->private_data;

}
@@ -576,6 +582,7 @@ void dma_buf_put(struct dma_buf *dmabuf) 
	if (WARN_ON(!dmabuf || !dmabuf->file))

		return;



	dma_buf_ref_mod(dmabuf, -1);

	fput(dmabuf->file);

}

EXPORT_SYMBOL_GPL(dma_buf_put);
@@ -1266,6 +1273,8 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) 
		seq_printf(s, "Total %d devices attached\n\n",

				attach_count);



		dma_buf_ref_show(s, buf_obj);



		count++;

		size += buf_obj->size;

		mutex_unlock(&buf_obj->lock);

include/linux/dma-buf-ref.h

0 → 100644
+36 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2018, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and

 * only version 2 as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */



#ifndef _DMA_BUF_REF_H

#define _DMA_BUF_REF_H



struct dma_buf;

struct seq_file;



#ifdef CONFIG_DEBUG_DMA_BUF_REF

void dma_buf_ref_init(struct dma_buf *b);

void dma_buf_ref_destroy(struct dma_buf *b);

void dma_buf_ref_mod(struct dma_buf *b, int nr);

int dma_buf_ref_show(struct seq_file *s, struct dma_buf *dmabuf);



#else

static inline void dma_buf_ref_init(struct dma_buf *b) {}

static inline void dma_buf_ref_destroy(struct dma_buf *b) {}

static inline void dma_buf_ref_mod(struct dma_buf *b, int nr) {}

static inline int dma_buf_ref_show(struct seq_file *s, struct dma_buf *dmabuf)

{

	return -ENOMEM;

}

#endif





#endif /* _DMA_BUF_REF_H */