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Commit 21b1ed74 authored by Albert Lee's avatar Albert Lee Committed by Jeff Garzik
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[PATCH] libata: Prevent the interrupt handler from completing a command twice 



Problem:
   During the libata CD-ROM stress test, sometimes the "BUG: timeout
without command" error is seen.

Root cause:
  Unexpected interrupt occurs after the ata_qc_complete() is called,
but before the SCSI error handler.  The interrupt handler is invoked
before the SCSI error handler, and it clears the command by calling
ata_qc_complete() again.  Later when the SCSI error handler is run,
the ata_queued_cmd is already gone, causing the "BUG: timeout without
command" error.

Changes:
  - Use the ATA_QCFLAG_ACTIVE flag to prevent the interrupt handler
from completing the command twice, before the scsi_error_handler.

Signed-off-by: default avatarAlbert Lee <albertcc@tw.ibm.com>
parent f85bdb9c

drivers/scsi/libata-core.c

+4 −2
Original line number Diff line number Diff line
@@ -2539,7 +2539,7 @@ static void atapi_request_sense(struct ata_port *ap, struct ata_device *dev, 
	ata_sg_init_one(qc, cmd->sense_buffer, sizeof(cmd->sense_buffer));

	qc->dma_dir = DMA_FROM_DEVICE;



	memset(&qc->cdb, 0, sizeof(ap->cdb_len));

	memset(&qc->cdb, 0, ap->cdb_len);

	qc->cdb[0] = REQUEST_SENSE;

	qc->cdb[4] = SCSI_SENSE_BUFFERSIZE;
@@ -2811,6 +2811,7 @@ void ata_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat) 


	/* call completion callback */

	rc = qc->complete_fn(qc, drv_stat);

	qc->flags &= ~ATA_QCFLAG_ACTIVE;



	/* if callback indicates not to complete command (non-zero),

	 * return immediately
@@ -3229,7 +3230,8 @@ irqreturn_t ata_interrupt (int irq, void *dev_instance, struct pt_regs *regs) 
			struct ata_queued_cmd *qc;



			qc = ata_qc_from_tag(ap, ap->active_tag);

			if (qc && (!(qc->tf.ctl & ATA_NIEN)))

			if (qc && (!(qc->tf.ctl & ATA_NIEN)) &&

			    (qc->flags & ATA_QCFLAG_ACTIVE))

				handled |= ata_host_intr(ap, qc);

		}

	}