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Subject[RFC, PATCH] ide-probe init_irq cleanup
Hi all,

init_irq calls request_irq while holding the ide_lock spinlock. This can
deadlock, because request_irq can sleep under some circumstances - e.g.
for the allocation of the /proc/irq entries, or for randomness
management structures.

The attached patch modifies init_irq and calls request_irq without the
spinlock held. It also fixes a potential race between choose_drive and
init_irq.

The patch is against 2.5.64-ac4, it should apply to 2.5.64 with some
offsets.


--
Manfred
// $Header$
// Kernel Version:
// VERSION = 2
// PATCHLEVEL = 5
// SUBLEVEL = 64
// EXTRAVERSION = -ac4
--- 2.5/include/linux/ide.h 2003-03-15 18:57:02.000000000 +0100
+++ build-2.5/include/linux/ide.h 2003-03-15 18:59:44.000000000 +0100
@@ -1740,6 +1740,19 @@
extern int ide_set_xfer_rate(ide_drive_t *drive, u8 rate);

extern spinlock_t ide_lock;
+extern struct semaphore ide_cfg_sem;
+/*
+ * Structure locking:
+ *
+ * ide_cfg_sem and ide_lock together protect changes to
+ * ide_hwif_t->{next,hwgroup}
+ * ide_drive_t->next
+ *
+ * ide_hwgroup_t->busy: ide_lock
+ * ide_hwgroup_t->hwif: ide_lock
+ * ide_hwif_t->mate: constant, no locking
+ * ide_drive_t->hwif: constant, no locking
+ */

#define local_irq_set(flags) do { local_save_flags((flags)); local_irq_enable(); } while (0)

--- 2.5/drivers/ide/ide-probe.c 2003-03-15 18:57:00.000000000 +0100
+++ build-2.5/drivers/ide/ide-probe.c 2003-03-17 21:52:44.000000000 +0100
@@ -1017,7 +1017,13 @@

/* This is a driver limit and could be eliminated. */
blk_queue_max_phys_segments(q, PRD_ENTRIES);
+}

+/*
+ * Setup the drive for request handling.
+ */
+static void ide_init_drive(ide_drive_t *drive)
+{
ide_toggle_bounce(drive, 1);

#ifdef CONFIG_BLK_DEV_IDE_TCQ_DEFAULT
@@ -1040,16 +1046,14 @@
*/
static int init_irq (ide_hwif_t *hwif)
{
- unsigned long flags;
unsigned int index;
- ide_hwgroup_t *hwgroup, *new_hwgroup;
+ ide_hwgroup_t *hwgroup;
ide_hwif_t *match = NULL;

- /* Allocate the buffer and potentially sleep first */
- new_hwgroup = kmalloc(sizeof(ide_hwgroup_t),GFP_KERNEL);
-
- spin_lock_irqsave(&ide_lock, flags);

+ BUG_ON(in_interrupt());
+ BUG_ON(irqs_disabled());
+ down(&ide_cfg_sem);
hwif->hwgroup = NULL;
#if MAX_HWIFS > 1
/*
@@ -1081,14 +1085,28 @@
*/
if (match) {
hwgroup = match->hwgroup;
- if(new_hwgroup)
- kfree(new_hwgroup);
+ hwif->hwgroup = hwgroup;
+ /*
+ * Link us into the hwgroup.
+ * This must be done early, do ensure that unexpected_intr
+ * can find the hwif and prevent irq storms.
+ * No drives are attached to the new hwif, choose_drive
+ * can't do anything stupid (yet).
+ * Add ourself as the 2nd entry to the hwgroup->hwif
+ * linked list, the first entry is the hwif that owns
+ * hwgroup->handler - do not change that.
+ */
+ spin_lock_irq(&ide_lock);
+ hwif->next = hwgroup->hwif->next;
+ hwgroup->hwif->next = hwif;
+ spin_unlock_irq(&ide_lock);
} else {
- hwgroup = new_hwgroup;
- if (!hwgroup) {
- spin_unlock_irqrestore(&ide_lock, flags);
- return 1;
- }
+ hwgroup = kmalloc(sizeof(ide_hwgroup_t),GFP_KERNEL);
+ if (!hwgroup)
+ goto out_up;
+
+ hwif->hwgroup = hwgroup;
+
memset(hwgroup, 0, sizeof(ide_hwgroup_t));
hwgroup->hwif = hwif->next = hwif;
hwgroup->rq = NULL;
@@ -1120,44 +1138,35 @@
/* clear nIEN */
hwif->OUTB(0x08, hwif->io_ports[IDE_CONTROL_OFFSET]);

- if (request_irq(hwif->irq,&ide_intr,sa,hwif->name,hwgroup)) {
- if (!match)
- kfree(hwgroup);
- spin_unlock_irqrestore(&ide_lock, flags);
- return 1;
- }
+ if (request_irq(hwif->irq,&ide_intr,sa,hwif->name,hwgroup))
+ goto out_unlink;
}

/*
- * Everything is okay, so link us into the hwgroup
+ * Link any new drives into the hwgroup, allocate
+ * the block device queue and initialize the drive.
+ * Note that ide_init_drive sends commands to the new
+ * drive.
*/
- hwif->hwgroup = hwgroup;
- hwif->next = hwgroup->hwif->next;
- hwgroup->hwif->next = hwif;
-
for (index = 0; index < MAX_DRIVES; ++index) {
ide_drive_t *drive = &hwif->drives[index];
if (!drive->present)
continue;
- if (!hwgroup->drive)
- hwgroup->drive = drive;
- drive->next = hwgroup->drive->next;
- hwgroup->drive->next = drive;
- spin_unlock_irqrestore(&ide_lock, flags);
ide_init_queue(drive);
- spin_lock_irqsave(&ide_lock, flags);
- }
-
- if (!hwgroup->hwif) {
- hwgroup->hwif = HWIF(hwgroup->drive);
-#ifdef DEBUG
- printk("%s : Adding missed hwif to hwgroup!!\n", hwif->name);
-#endif
+ spin_lock_irq(&ide_lock);
+ if (!hwgroup->drive) {
+ /* first drive for hwgroup. */
+ drive->next = drive;
+ hwgroup->drive = drive;
+ hwgroup->hwif = HWIF(hwgroup->drive);
+ } else {
+ drive->next = hwgroup->drive->next;
+ hwgroup->drive->next = drive;
+ }
+ spin_unlock_irq(&ide_lock);
+ ide_init_drive(drive);
}

- /* all CPUs; safe now that hwif->hwgroup is set up */
- spin_unlock_irqrestore(&ide_lock, flags);
-
#if !defined(__mc68000__) && !defined(CONFIG_APUS) && !defined(__sparc__)
printk("%s at 0x%03lx-0x%03lx,0x%03lx on irq %d", hwif->name,
hwif->io_ports[IDE_DATA_OFFSET],
@@ -1176,6 +1185,30 @@
printk(" (%sed with %s)",
hwif->sharing_irq ? "shar" : "serializ", match->name);
printk("\n");
+ up(&ide_cfg_sem);
+ return 0;
+out_unlink:
+ spin_lock_irq(&ide_lock);
+ if (hwif->next == hwif) {
+ BUG_ON(match);
+ BUG_ON(hwgroup->hwif != hwif);
+ kfree(hwgroup);
+ } else {
+ ide_hwif_t *g;
+ g = hwgroup->hwif;
+ while (g->next != hwif)
+ g = g->next;
+ g->next = hwif->next;
+ if (hwgroup->hwif == hwif) {
+ /* Impossible. */
+ printk(KERN_ERR "Duh. Uninitialized hwif listed as active hwif.\n");
+ hwgroup->hwif = g;
+ }
+ BUG_ON(hwgroup->hwif == hwif);
+ }
+ spin_unlock_irq(&ide_lock);
+out_up:
+ up(&ide_cfg_sem);
return 0;
}

@@ -1351,6 +1384,7 @@
void export_ide_init_queue (ide_drive_t *drive)
{
ide_init_queue(drive);
+ ide_init_drive(drive);
}

EXPORT_SYMBOL(export_ide_init_queue);
--- 2.5/drivers/ide/ide.c 2003-03-15 18:57:00.000000000 +0100
+++ build-2.5/drivers/ide/ide.c 2003-03-15 18:59:44.000000000 +0100
@@ -177,6 +177,7 @@
static int system_bus_speed; /* holds what we think is VESA/PCI bus speed */
static int initializing; /* set while initializing built-in drivers */

+DECLARE_MUTEX(ide_cfg_sem);
spinlock_t ide_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;

static int ide_scan_direction; /* THIS was formerly 2.2.x pci=reverse */
@@ -582,17 +583,19 @@

void ide_unregister (unsigned int index)
{
- ide_drive_t *drive, *d;
+ ide_drive_t *drive;
ide_hwif_t *hwif, *g;
ide_hwgroup_t *hwgroup;
int irq_count = 0, unit, i;
- unsigned long flags;
ide_hwif_t old_hwif;

if (index >= MAX_HWIFS)
BUG();

- spin_lock_irqsave(&ide_lock, flags);
+ BUG_ON(in_interrupt());
+ BUG_ON(irqs_disabled());
+ down(&ide_cfg_sem);
+ spin_lock_irq(&ide_lock);
hwif = &ide_hwifs[index];
if (!hwif->present)
goto abort;
@@ -607,7 +610,7 @@
}
hwif->present = 0;

- spin_unlock_irqrestore(&ide_lock, flags);
+ spin_unlock_irq(&ide_lock);

for (unit = 0; unit < MAX_DRIVES; ++unit) {
drive = &hwif->drives[unit];
@@ -619,7 +622,6 @@
#ifdef CONFIG_PROC_FS
destroy_proc_ide_drives(hwif);
#endif
- spin_lock_irqsave(&ide_lock, flags);
hwgroup = hwif->hwgroup;

/*
@@ -634,6 +636,7 @@
if (irq_count == 1)
free_irq(hwif->irq, hwgroup);

+ spin_lock_irq(&ide_lock);
/*
* Note that we only release the standard ports,
* and do not even try to handle any extra ports
@@ -645,7 +648,6 @@
* Remove us from the hwgroup, and free
* the hwgroup if we were the only member
*/
- d = hwgroup->drive;
for (i = 0; i < MAX_DRIVES; ++i) {
drive = &hwif->drives[i];
if (drive->de) {
@@ -654,11 +656,23 @@
}
if (!drive->present)
continue;
- while (hwgroup->drive->next != drive)
- hwgroup->drive = hwgroup->drive->next;
- hwgroup->drive->next = drive->next;
- if (hwgroup->drive == drive)
+ if (drive == drive->next) {
+ /* special case: last drive from hwgroup. */
+ BUG_ON(hwgroup->drive != drive);
hwgroup->drive = NULL;
+ } else {
+ ide_drive_t *walk;
+
+ walk = hwgroup->drive;
+ while (walk->next != drive)
+ walk = walk->next;
+ walk->next = drive->next;
+ if (hwgroup->drive == drive) {
+ hwgroup->drive = drive->next;
+ hwgroup->hwif = HWIF(hwgroup->drive);
+ }
+ }
+ BUG_ON(hwgroup->drive == drive);
if (drive->id != NULL) {
kfree(drive->id);
drive->id = NULL;
@@ -666,15 +680,28 @@
drive->present = 0;
blk_cleanup_queue(&drive->queue);
}
- if (d->present)
- hwgroup->drive = d;
- while (hwgroup->hwif->next != hwif)
- hwgroup->hwif = hwgroup->hwif->next;
- hwgroup->hwif->next = hwif->next;
- if (hwgroup->hwif == hwif)
+ if (hwif->next == hwif) {
kfree(hwgroup);
- else
- hwgroup->hwif = HWIF(hwgroup->drive);
+ BUG_ON(hwgroup->hwif != hwif);
+ } else {
+ /* There is another interface in hwgroup.
+ * Unlink us, and set hwgroup->drive and ->hwif to
+ * something sane.
+ */
+ g = hwgroup->hwif;
+ while (g->next != hwif)
+ g = g->next;
+ g->next = hwif->next;
+ if (hwgroup->hwif == hwif) {
+ /* Chose a random hwif for hwgroup->hwif.
+ * It's guaranteed that there are no drives
+ * left in the hwgroup.
+ */
+ BUG_ON(hwgroup->drive != NULL);
+ hwgroup->hwif = g;
+ }
+ BUG_ON(hwgroup->hwif == hwif);
+ }

#if !defined(CONFIG_DMA_NONPCI)
if (hwif->dma_base) {
@@ -814,7 +841,8 @@

hwif->hwif_data = old_hwif.hwif_data;
abort:
- spin_unlock_irqrestore(&ide_lock, flags);
+ spin_unlock_irq(&ide_lock);
+ up(&ide_cfg_sem);
}

EXPORT_SYMBOL(ide_unregister);
--- 2.5/drivers/ide/ide-io.c 2003-03-15 18:57:00.000000000 +0100
+++ build-2.5/drivers/ide/ide-io.c 2003-03-15 18:59:44.000000000 +0100
@@ -771,8 +771,8 @@
/* for atari only: POSSIBLY BROKEN HERE(?) */
ide_get_lock(ide_intr, hwgroup);

- /* necessary paranoia: ensure IRQs are masked on local CPU */
- local_irq_disable();
+ /* caller must own ide_lock */
+ BUG_ON(!irqs_disabled());

while (!hwgroup->busy) {
hwgroup->busy = 1;
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