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SubjectRe: PATCH: [2.4.21-pre3] Fix for SMP race condition in IDE code

Ross,

Sheesh, I know who is a candiated for me to dump the maintainership on in
the future! This will take a little time to reveiw; however, I know of no
one who runs systems in this scale.

Also "t" is the last drive.

If you need more drives, use the upper half of the current majors
/dev/hdu 3,128
/dev/hdv 3,192

Repeat ... that will make it to 20 channels.

Cheers,


On Fri, 10 Jan 2003, Ross Biro wrote:

>
> There is a race condition in all versions of the IDE code that I've
> looked at including 2.4.18 and 2.4.21-pre3. Basically on an SMP system
> if mutiple IDE channels are on the same interrupt and 1 channel sends
> has an interrupt pending on 1 processor while the other processor is
> calling ide_set_handler, then the interrupt can be mistaken for command
> completion on both channels, and a command can be completed before it is
> even issued.
>
> This problem can be triggered with the following code
>
> cd /proc/ide
> (while true; do for i in hd[a-z]; do for j in 1 2 3 ; do cat
> $i/smart_values >/dev/null; done; done; done) &
> (while true; do for i in hd[a-z]; do dd if=/dev/$i of=/dev/null bs=4096k
> skip=0 & done; wait; done) &
>
> And can be seen by properly instrumenting drive_cmd_intr to check for
> errors.
>
> On a dual proc machine with 4 channels on a single interrupt and 2.4.18
> I expec to see an error about once every twenty minutes with the above
> code. I believe it should occur much less often on 2.4.20 and above.
>
> Drives react to this problem in different ways. Often they simply lock
> up and refuse to talk to the host until they have been properly reset.
> Some drives require a power cycle before they will work properly again.
>
> This problem required the use of over 200 machines, approximately 2000
> drives, a bus analyzer, and a lot of cooperation from a couple of drive
> manufacturers to go from "something goes wrong once in a while" to
> something we could easily reproduce.
>
> This patch has only been minimally tested and then only with 1 brand of
> ide hard drive.
>
> ----- snip ------
>
> diff -durbB linux-2.4.20/drivers/ide/ide-cd.c
> linux-2.4.20-p1/drivers/ide/ide-cd.c
> --- linux-2.4.20/drivers/ide/ide-cd.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-cd.c Wed Jan 8 16:25:04 2003
> @@ -863,11 +864,15 @@
> HWIF(drive)->OUTB(drive->ctl, IDE_CONTROL_REG);
>
> if (CDROM_CONFIG_FLAGS (drive)->drq_interrupt) {
> + unsigned long flags;
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler (drive, handler, WAIT_CMD, cdrom_timer_expiry);
> + spin_lock_irqsave(&io_request_lock, flags);
> /* packet command */
> HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> + ide_set_handler_nolock (drive, handler, WAIT_CMD,
> cdrom_timer_expiry);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
> return ide_started;
> } else {
> /* packet command */
> diff -durbB linux-2.4.20/drivers/ide/ide-disk.c
> linux-2.4.20-p1/drivers/ide/ide-disk.c
> --- linux-2.4.20/drivers/ide/ide-disk.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-disk.c Wed Jan 8 16:25:17 2003
> @@ -467,12 +467,15 @@
> #endif /* CONFIG_BLK_DEV_IDEDMA */
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler(drive, &read_intr, WAIT_CMD, NULL);
>
> command = ((drive->mult_count) ?
> ((lba48) ? WIN_MULTREAD_EXT : WIN_MULTREAD) :
> ((lba48) ? WIN_READ_EXT : WIN_READ));
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(command, IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive, &read_intr, WAIT_CMD, NULL);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
> return ide_started;
> } else if (rq_data_dir(rq) == WRITE) {
> ide_startstop_t startstop;
> diff -durbB linux-2.4.20/drivers/ide/ide-dma.c
> linux-2.4.20-p1/drivers/ide/ide-dma.c
> --- linux-2.4.20/drivers/ide/ide-dma.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-dma.c Thu Jan 9 15:32:09 2003
> @@ -655,6 +655,7 @@
> unsigned int count = 0;
> u8 dma_stat = 0, lba48 = (drive->addressing == 1) ? 1 : 0;
> task_ioreg_t command = WIN_NOP;
> + unsigned long flags;
>
> if (!(count = ide_build_dmatable(drive, rq, PCI_DMA_FROMDEVICE)))
> /* try PIO instead of DMA */
> @@ -673,7 +674,6 @@
> /* paranoia check */
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler(drive, &ide_dma_intr, 2*WAIT_CMD, dma_timer_expiry);
>
> /*
> * FIX ME to use only ACB ide_task_t args Struct
> @@ -691,7 +691,11 @@
> }
> #endif
> /* issue cmd to drive */
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(command, IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive, &ide_dma_intr, 2*WAIT_CMD,
> dma_timer_expiry);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
>
> return HWIF(drive)->ide_dma_count(drive);
> }
> @@ -707,6 +711,7 @@
> unsigned int count = 0;
> u8 dma_stat = 0, lba48 = (drive->addressing == 1) ? 1 : 0;
> task_ioreg_t command = WIN_NOP;
> + unsigned long flags;
>
> if (!(count = ide_build_dmatable(drive, rq, PCI_DMA_TODEVICE)))
> /* try PIO instead of DMA */
> @@ -725,7 +730,6 @@
> /* paranoia check */
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler(drive, &ide_dma_intr, 2*WAIT_CMD, dma_timer_expiry);
> /*
> * FIX ME to use only ACB ide_task_t args Struct
> */
> @@ -742,7 +746,13 @@
> }
> #endif
> /* issue cmd to drive */
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(command, IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive, &ide_dma_intr,
> + 2*WAIT_CMD, dma_timer_expiry);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
> +
> return HWIF(drive)->ide_dma_count(drive);
> }
>
> diff -durbB linux-2.4.20/drivers/ide/ide-floppy.c
> linux-2.4.20-p1/drivers/ide/ide-floppy.c
> --- linux-2.4.20/drivers/ide/ide-floppy.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-floppy.c Wed Jan 8 16:15:17 2003
> @@ -1123,14 +1123,17 @@
> }
>
> if (test_bit(IDEFLOPPY_DRQ_INTERRUPT, &floppy->flags)) {
> + unsigned long flags;
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> + /* Issue the packet command */
> + spin_lock_irqsave(&io_request_lock, flags);
> + HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> ide_set_handler(drive,
> pkt_xfer_routine,
> IDEFLOPPY_WAIT_CMD,
> NULL);
> - /* Issue the packet command */
> - HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> + spin_unlock_irqrestore(&io_request_lock, flags);
> return ide_started;
> } else {
> /* Issue the packet command */
> diff -durbB linux-2.4.20/drivers/ide/ide-io.c
> linux-2.4.20-p1/drivers/ide/ide-io.c
> --- linux-2.4.20/drivers/ide/ide-io.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-io.c Wed Jan 8 16:25:37 2003
> @@ -363,14 +363,21 @@
> void ide_cmd (ide_drive_t *drive, u8 cmd, u8 nsect, ide_handler_t *handler)
> {
> ide_hwif_t *hwif = HWIF(drive);
> + unsigned long flags;
> +
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler(drive, handler, WAIT_CMD, NULL);
> if (IDE_CONTROL_REG)
> hwif->OUTB(drive->ctl,IDE_CONTROL_REG); /* clear nIEN */
> SELECT_MASK(drive,0);
> hwif->OUTB(nsect,IDE_NSECTOR_REG);
> +
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(cmd,IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive, handler, WAIT_CMD, NULL);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
> +
> }
>
> EXPORT_SYMBOL(ide_cmd);
> diff -durbB linux-2.4.20/drivers/ide/ide-iops.c
> linux-2.4.20-p1/drivers/ide/ide-iops.c
> --- linux-2.4.20/drivers/ide/ide-iops.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-iops.c Wed Jan 8 15:54:18 2003
> @@ -908,13 +908,14 @@
> * timer is started to prevent us from waiting forever in case
> * something goes wrong (see the ide_timer_expiry() handler later on).
> */
> -void ide_set_handler (ide_drive_t *drive, ide_handler_t *handler,
> +
> +/* This version doesn't get the spinlock, so you must call it with a
> spinlock
> + on io_request_lock. */
> +void ide_set_handler_nolock (ide_drive_t *drive, ide_handler_t *handler,
> unsigned int timeout, ide_expiry_t *expiry)
> {
> - unsigned long flags;
> ide_hwgroup_t *hwgroup = HWGROUP(drive);
>
> - spin_lock_irqsave(&io_request_lock, flags);
> if (hwgroup->handler != NULL) {
> printk("%s: ide_set_handler: handler not null; "
> "old=%p, new=%p\n",
> @@ -924,6 +925,15 @@
> hwgroup->expiry = expiry;
> hwgroup->timer.expires = jiffies + timeout;
> add_timer(&hwgroup->timer);
> +}
> +
> +/* This version grabs and releases the io_request_lock, so must be called
> + with out the spinlock grabbed. */
> +void ide_set_handler (ide_drive_t *drive, ide_handler_t *handler,
> + unsigned int timeout, ide_expiry_t *expiry) {
> + unsigned long flags;
> + spin_lock_irqsave(&io_request_lock, flags);
> + ide_set_handler_nolock(drive, handler, timeout, expiry);
> spin_unlock_irqrestore(&io_request_lock, flags);
> }
>
> diff -durbB linux-2.4.20/drivers/ide/ide-tape.c
> linux-2.4.20-p1/drivers/ide/ide-tape.c
> --- linux-2.4.20/drivers/ide/ide-tape.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-tape.c Wed Jan 8 16:20:09 2003
> @@ -2457,13 +2457,17 @@
> set_bit(PC_DMA_IN_PROGRESS, &pc->flags);
> #endif /* CONFIG_BLK_DEV_IDEDMA */
> if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
> + unsigned long flags;
> if (HWGROUP(drive)->handler != NULL)
> BUG();
> - ide_set_handler(drive,
> +
> + spin_lock_irqsave(&io_request_lock, flags);
> + HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive,
> &idetape_transfer_pc,
> IDETAPE_WAIT_CMD,
> NULL);
> - HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> + spin_unlock_irqrestore(&io_request_lock, flags);
> return ide_started;
> } else {
> HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> diff -durbB linux-2.4.20/drivers/ide/ide-taskfile.c
> linux-2.4.20-p1/drivers/ide/ide-taskfile.c
> --- linux-2.4.20/drivers/ide/ide-taskfile.c Thu Jan 9 11:14:01 2003
> +++ linux-2.4.20-p1/drivers/ide/ide-taskfile.c Wed Jan 8 16:25:43 2003
> @@ -173,6 +173,7 @@
> task_struct_t *taskfile = (task_struct_t *) task->tfRegister;
> hob_struct_t *hobfile = (hob_struct_t *) task->hobRegister;
> u8 HIHI = (drive->addressing == 1) ? 0xE0 : 0xEF;
> + unsigned long flags;
>
> #ifdef CONFIG_IDE_TASK_IOCTL_DEBUG
> void debug_taskfile(drive, task);
> @@ -201,8 +202,14 @@
>
> hwif->OUTB((taskfile->device_head & HIHI) | drive->select.all,
> IDE_SELECT_REG);
> if (task->handler != NULL) {
> - ide_set_handler(drive, task->handler, WAIT_WORSTCASE, NULL);
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(taskfile->command, IDE_COMMAND_REG);
> + /* We need to give the drive time to set the busy
> + flag, or we may mistake an interrupt from another drive
> + for the command completion on this drive. */
> + ide_set_handler_nolock(drive, task->handler, WAIT_WORSTCASE, NULL);
> + ide_delay_400ns();
> + spin_unlock_irqrestore(&io_request_lock, flags);
> if (task->prehandler != NULL)
> return task->prehandler(drive, task->rq);
> return ide_started;
> @@ -1832,6 +1839,7 @@
> ide_hwif_t *hwif = HWIF(drive);
> task_struct_t *taskfile = (task_struct_t *) task->tfRegister;
> hob_struct_t *hobfile = (hob_struct_t *) task->hobRegister;
> + unsigned long flags;
> #if DEBUG_TASKFILE
> u8 status;
> #endif
> @@ -1929,9 +1937,13 @@
> if (task->handler == NULL)
> return ide_stopped;
>
> - ide_set_handler(drive, task->handler, WAIT_WORSTCASE, NULL);
> +
> /* Issue the command */
> + spin_lock_irqsave(&io_request_lock, flags);
> hwif->OUTB(taskfile->command, IDE_COMMAND_REG);
> + ide_set_handler_nolock(drive, task->handler,
> + WAIT_WORSTCASE, NULL);
> + spin_unlock_irqrestore(&io_request_lock, flags);
> if (task->prehandler != NULL)
> return task->prehandler(drive, HWGROUP(drive)->rq);
> }
> diff -durbB linux-2.4.20/include/asm-i386/ide.h
> linux-2.4.20-p1/include/asm-i386/ide.h
> --- linux-2.4.20/include/asm-i386/ide.h Thu Jan 9 11:17:05 2003
> +++ linux-2.4.20-p1/include/asm-i386/ide.h Fri Jan 10 09:54:07 2003
> @@ -14,6 +14,7 @@
> #ifdef __KERNEL__
>
> #include <linux/config.h>
> +#include <linux/delay.h>
>
> #ifndef MAX_HWIFS
> # ifdef CONFIG_BLK_DEV_IDEPCI
> @@ -22,6 +23,16 @@
> #define MAX_HWIFS 6
> # endif
> #endif
> +
> +
> +
> +/* The ATA spec requires 400ns delays all over the place. */
> +/* Do the same fixed point trick the udelay does to get our delay. */
> +#define IDE_DELAY_400NS
> +static __inline__ void ide_delay_400ns(void)
> +{
> + __const_udelay (400 * 4);
> +}
>
> static __inline__ int ide_default_irq(ide_ioreg_t base)
> {
> diff -durbB linux-2.4.20/include/linux/ide.h
> linux-2.4.20-p1/include/linux/ide.h
> --- linux-2.4.20/include/linux/ide.h Thu Jan 9 11:17:05 2003
> +++ linux-2.4.20-p1/include/linux/ide.h Thu Jan 9 15:37:22 2003
> @@ -18,6 +18,7 @@
> #include <linux/bitops.h>
> #include <linux/highmem.h>
> #include <linux/pci.h>
> +#include <linux/delay.h>
> #include <asm/byteorder.h>
> #include <asm/system.h>
> #include <asm/hdreg.h>
> @@ -354,6 +355,11 @@
>
> #include <asm/ide.h>
>
> +#ifndef IDE_DELAY_400NS
> +#define IDE_DELAY_400NS
> +static inline void ide_delay_400ns(void) { udelay(1); }
> +#endif
> +
> /* Currently only m68k, apus and m8xx need it */
> #ifdef IDE_ARCH_ACK_INTR
> extern int ide_irq_lock;
> @@ -1282,6 +1288,7 @@
> * and also to start the safety timer.
> */
> extern void ide_set_handler(ide_drive_t *, ide_handler_t *, unsigned
> int, ide_expiry_t *);
> +extern void ide_set_handler_nolock(ide_drive_t *, ide_handler_t *,
> unsigned int, ide_expiry_t *);
>
> /*
> * Error reporting, in human readable form (luxurious, but a memory hog).
>
>

Andre Hedrick
LAD Storage Consulting Group

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