mirror of https://gitee.com/openkylin/linux.git
atari_scsi: Fix atari_scsi deadlocks on Falcon
Don't disable irqs when waiting for the ST DMA "lock"; its release may require an interrupt. Introduce stdma_try_lock() for use in soft irq context. atari_scsi now tells the SCSI mid-layer to defer queueing a command if the ST DMA lock is not available, as per Michael's patch: http://marc.info/?l=linux-m68k&m=139095335824863&w=2 The falcon_got_lock variable is race prone: we can't disable IRQs while waiting to acquire the lock, so after acquiring it there must be some interval during which falcon_got_lock remains false. Introduce stdma_is_locked_by() to replace falcon_got_lock. The falcon_got_lock tests in the EH handlers are incorrect these days. It can happen that an EH handler is called after a command completes normally. Remove these checks along with falcon_got_lock. Also remove the complicated and racy fairness wait queues. If fairness is an issue (when SCSI competes with IDE for the ST DMA interrupt), the solution is likely to be a lower value for host->can_queue. Signed-off-by: Finn Thain <fthain@telegraphics.com.au> Reviewed-by: Hannes Reinecke <hare@suse.de> Tested-by: Michael Schmitz <schmitzmic@gmail.com> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Finn Thain
Christoph Hellwig
parent
cbad48deb3
commit
16b29e75a7
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@ -59,6 +59,31 @@ static irqreturn_t stdma_int (int irq, void *dummy);
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/************************* End of Prototypes **************************/
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/**
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* stdma_try_lock - attempt to acquire ST DMA interrupt "lock"
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* @handler: interrupt handler to use after acquisition
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*
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* Returns !0 if lock was acquired; otherwise 0.
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*/
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int stdma_try_lock(irq_handler_t handler, void *data)
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{
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unsigned long flags;
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local_irq_save(flags);
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if (stdma_locked) {
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local_irq_restore(flags);
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return 0;
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}
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stdma_locked = 1;
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stdma_isr = handler;
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stdma_isr_data = data;
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local_irq_restore(flags);
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return 1;
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}
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EXPORT_SYMBOL(stdma_try_lock);
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/*
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* Function: void stdma_lock( isrfunc isr, void *data )
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@ -78,19 +103,10 @@ static irqreturn_t stdma_int (int irq, void *dummy);
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void stdma_lock(irq_handler_t handler, void *data)
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{
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unsigned long flags;
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local_irq_save(flags); /* protect lock */
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/* Since the DMA is used for file system purposes, we
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have to sleep uninterruptible (there may be locked
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buffers) */
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wait_event(stdma_wait, !stdma_locked);
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stdma_locked = 1;
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stdma_isr = handler;
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stdma_isr_data = data;
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local_irq_restore(flags);
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wait_event(stdma_wait, stdma_try_lock(handler, data));
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}
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EXPORT_SYMBOL(stdma_lock);
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@ -122,22 +138,25 @@ void stdma_release(void)
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EXPORT_SYMBOL(stdma_release);
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/*
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* Function: int stdma_others_waiting( void )
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*
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* Purpose: Check if someone waits for the ST-DMA lock.
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*
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* Inputs: none
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*
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* Returns: 0 if no one is waiting, != 0 otherwise
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/**
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* stdma_is_locked_by - allow lock holder to check whether it needs to release.
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* @handler: interrupt handler previously used to acquire lock.
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*
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* Returns !0 if locked for the given handler; 0 otherwise.
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*/
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int stdma_others_waiting(void)
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int stdma_is_locked_by(irq_handler_t handler)
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{
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return waitqueue_active(&stdma_wait);
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unsigned long flags;
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int result;
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local_irq_save(flags);
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result = stdma_locked && (stdma_isr == handler);
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local_irq_restore(flags);
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return result;
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}
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EXPORT_SYMBOL(stdma_others_waiting);
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EXPORT_SYMBOL(stdma_is_locked_by);
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/*
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@ -8,11 +8,11 @@
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/***************************** Prototypes *****************************/
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int stdma_try_lock(irq_handler_t, void *);
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void stdma_lock(irq_handler_t handler, void *data);
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void stdma_release( void );
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int stdma_others_waiting( void );
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int stdma_islocked( void );
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void *stdma_locked_by( void );
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int stdma_is_locked_by(irq_handler_t);
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void stdma_init( void );
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/************************* End of Prototypes **************************/
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@ -879,10 +879,10 @@ static void NCR5380_exit(struct Scsi_Host *instance)
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*
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*/
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static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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void (*done)(struct scsi_cmnd *))
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static int NCR5380_queue_command(struct Scsi_Host *instance,
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struct scsi_cmnd *cmd)
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{
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SETUP_HOSTDATA(cmd->device->host);
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struct NCR5380_hostdata *hostdata = shost_priv(instance);
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struct scsi_cmnd *tmp;
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unsigned long flags;
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@ -893,7 +893,7 @@ static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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printk(KERN_NOTICE "scsi%d: WRITE attempted with NO_WRITE debugging flag set\n",
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H_NO(cmd));
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cmd->result = (DID_ERROR << 16);
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done(cmd);
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cmd->scsi_done(cmd);
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return 0;
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}
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#endif /* (NDEBUG & NDEBUG_NO_WRITE) */
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@ -904,8 +904,6 @@ static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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*/
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SET_NEXT(cmd, NULL);
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cmd->scsi_done = done;
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cmd->result = 0;
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/*
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@ -915,7 +913,6 @@ static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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* sense data is only guaranteed to be valid while the condition exists.
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*/
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local_irq_save(flags);
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/* ++guenther: now that the issue queue is being set up, we can lock ST-DMA.
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* Otherwise a running NCR5380_main may steal the lock.
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* Lock before actually inserting due to fairness reasons explained in
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@ -928,11 +925,11 @@ static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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* because also a timer int can trigger an abort or reset, which would
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* alter queues and touch the lock.
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*/
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if (!IS_A_TT()) {
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/* perhaps stop command timer here */
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falcon_get_lock();
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/* perhaps restart command timer here */
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}
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if (!falcon_get_lock())
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return SCSI_MLQUEUE_HOST_BUSY;
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local_irq_save(flags);
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if (!(hostdata->issue_queue) || (cmd->cmnd[0] == REQUEST_SENSE)) {
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LIST(cmd, hostdata->issue_queue);
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SET_NEXT(cmd, hostdata->issue_queue);
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@ -956,15 +953,13 @@ static int NCR5380_queue_command_lck(struct scsi_cmnd *cmd,
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* If we're not in an interrupt, we can call NCR5380_main()
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* unconditionally, because it cannot be already running.
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*/
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if (in_interrupt() || ((flags >> 8) & 7) >= 6)
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if (in_interrupt() || irqs_disabled())
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queue_main();
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else
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NCR5380_main(NULL);
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return 0;
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}
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static DEF_SCSI_QCMD(NCR5380_queue_command)
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/*
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* Function : NCR5380_main (void)
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*
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@ -2554,10 +2549,6 @@ int NCR5380_abort(struct scsi_cmnd *cmd)
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local_irq_save(flags);
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if (!IS_A_TT() && !falcon_got_lock)
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printk(KERN_ERR "scsi%d: !!BINGO!! Falcon has no lock in NCR5380_abort\n",
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HOSTNO);
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dprintk(NDEBUG_ABORT, "scsi%d: abort called basr 0x%02x, sr 0x%02x\n", HOSTNO,
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NCR5380_read(BUS_AND_STATUS_REG),
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NCR5380_read(STATUS_REG));
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@ -2756,10 +2747,6 @@ static int NCR5380_bus_reset(struct scsi_cmnd *cmd)
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struct scsi_cmnd *connected, *disconnected_queue;
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#endif
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if (!IS_A_TT() && !falcon_got_lock)
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printk(KERN_ERR "scsi%d: !!BINGO!! Falcon has no lock in NCR5380_reset\n",
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H_NO(cmd));
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NCR5380_print_status(cmd->device->host);
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/* get in phase */
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@ -184,7 +184,7 @@ static void atari_scsi_fetch_restbytes(void);
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static irqreturn_t scsi_tt_intr(int irq, void *dummy);
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static irqreturn_t scsi_falcon_intr(int irq, void *dummy);
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static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata);
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static void falcon_get_lock(void);
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static int falcon_get_lock(void);
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#ifdef CONFIG_ATARI_SCSI_RESET_BOOT
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static void atari_scsi_reset_boot(void);
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#endif
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@ -473,17 +473,10 @@ static void atari_scsi_fetch_restbytes(void)
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#endif /* REAL_DMA */
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static int falcon_got_lock = 0;
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static DECLARE_WAIT_QUEUE_HEAD(falcon_fairness_wait);
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static int falcon_trying_lock = 0;
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static DECLARE_WAIT_QUEUE_HEAD(falcon_try_wait);
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static int falcon_dont_release = 0;
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/* This function releases the lock on the DMA chip if there is no
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* connected command and the disconnected queue is empty. On
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* releasing, instances of falcon_get_lock are awoken, that put
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* themselves to sleep for fairness. They can now try to get the lock
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* again (but others waiting longer more probably will win).
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* connected command and the disconnected queue is empty.
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*/
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static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata)
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@ -495,20 +488,12 @@ static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata)
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local_irq_save(flags);
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if (falcon_got_lock && !hostdata->disconnected_queue &&
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!hostdata->issue_queue && !hostdata->connected) {
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if (falcon_dont_release) {
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#if 0
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printk("WARNING: Lock release not allowed. Ignored\n");
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#endif
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local_irq_restore(flags);
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return;
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}
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falcon_got_lock = 0;
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if (!hostdata->disconnected_queue &&
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!hostdata->issue_queue &&
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!hostdata->connected &&
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!falcon_dont_release &&
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stdma_is_locked_by(scsi_falcon_intr))
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stdma_release();
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wake_up(&falcon_fairness_wait);
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}
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local_irq_restore(flags);
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}
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@ -517,51 +502,19 @@ static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata)
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* If the DMA isn't locked already for SCSI, it tries to lock it by
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* calling stdma_lock(). But if the DMA is locked by the SCSI code and
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* there are other drivers waiting for the chip, we do not issue the
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* command immediately but wait on 'falcon_fairness_queue'. We will be
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* waked up when the DMA is unlocked by some SCSI interrupt. After that
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* we try to get the lock again.
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* But we must be prepared that more than one instance of
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* falcon_get_lock() is waiting on the fairness queue. They should not
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* try all at once to call stdma_lock(), one is enough! For that, the
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* first one sets 'falcon_trying_lock', others that see that variable
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* set wait on the queue 'falcon_try_wait'.
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* Complicated, complicated.... Sigh...
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* command immediately but tell the SCSI mid-layer to defer.
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*/
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static void falcon_get_lock(void)
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static int falcon_get_lock(void)
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{
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unsigned long flags;
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if (IS_A_TT())
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return;
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return 1;
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local_irq_save(flags);
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if (in_interrupt())
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return stdma_try_lock(scsi_falcon_intr, NULL);
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wait_event_cmd(falcon_fairness_wait,
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in_interrupt() || !falcon_got_lock || !stdma_others_waiting(),
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local_irq_restore(flags),
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local_irq_save(flags));
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while (!falcon_got_lock) {
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if (in_irq())
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panic("Falcon SCSI hasn't ST-DMA lock in interrupt");
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if (!falcon_trying_lock) {
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falcon_trying_lock = 1;
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stdma_lock(scsi_falcon_intr, NULL);
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falcon_got_lock = 1;
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falcon_trying_lock = 0;
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wake_up(&falcon_try_wait);
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} else {
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wait_event_cmd(falcon_try_wait,
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falcon_got_lock && !falcon_trying_lock,
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local_irq_restore(flags),
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local_irq_save(flags));
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}
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}
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local_irq_restore(flags);
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if (!falcon_got_lock)
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panic("Falcon SCSI: someone stole the lock :-(\n");
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stdma_lock(scsi_falcon_intr, NULL);
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return 1;
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}
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