xfs: buffer ->bi_end_io function requires irq-safe lock

Reports have surfaced of a lockdep splat complaining about an
irq-safe -> irq-unsafe locking order in the xfs_buf_bio_end_io() bio
completion handler. This only occurs when I/O errors are present
because bp->b_lock is only acquired in this context to protect
setting an error on the buffer. The problem is that this lock can be
acquired with the (request_queue) q->queue_lock held. See
scsi_end_request() or ata_qc_schedule_eh(), for example.

Replace the locked test/set of b_io_error with a cmpxchg() call.
This eliminates the need for the lock and thus the lock ordering
problem goes away.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

path: root/include/soc/at91/atmel-sfr.h

/*
 * Atmel SFR (Special Function Registers) register offsets and bit definitions.
 *
 * Copyright (C) 2016 Atmel
 *
 * Author: Ludovic Desroches <ludovic.desroches@atmel.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#ifndef _LINUX_MFD_SYSCON_ATMEL_SFR_H
#define _LINUX_MFD_SYSCON_ATMEL_SFR_H

#define AT91_SFR_DDRCFG		0x04	/* DDR Configuration Register */
/* 0x08 ~ 0x0c: Reserved */
#define AT91_SFR_OHCIICR	0x10	/* OHCI INT Configuration Register */
#define AT91_SFR_OHCIISR	0x14	/* OHCI INT Status Register */
#define AT91_SFR_I2SCLKSEL	0x90	/* I2SC Register */

/* Field definitions */
#define AT91_OHCIICR_SUSPEND_A	BIT(8)
#define AT91_OHCIICR_SUSPEND_B	BIT(9)
#define AT91_OHCIICR_SUSPEND_C	BIT(10)

#define AT91_OHCIICR_USB_SUSPEND	(AT91_OHCIICR_SUSPEND_A | \
					 AT91_OHCIICR_SUSPEND_B | \
					 AT91_OHCIICR_SUSPEND_C)


#endif /* _LINUX_MFD_SYSCON_ATMEL_SFR_H */