Use stop_machine_run in the Intel RNG driver

Replace call_smp_function with stop_machine_run in the Intel RNG driver.

CPU A has done read_lock(&lock)
CPU B has done write_lock_irq(&lock) and is waiting for A to release the lock.

A third CPU calls call_smp_function and issues the IPI.  CPU A takes CPU
C's IPI.  CPU B is waiting with interrupts disabled and does not see the
IPI.  CPU C is stuck waiting for CPU B to respond to the IPI.

Deadlock.

The solution is to use stop_machine_run instead of call_smp_function
(call_smp_function should not be called in situations where the CPUs may be
suspended).

[haruo.tomita@toshiba.co.jp: fix a typo in mod_init()]
[haruo.tomita@toshiba.co.jp: fix memory leak]
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: "Tomita, Haruo" <haruo.tomita@toshiba.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 127 insertions, 100 deletions

diff --git a/drivers/char/hw_random/intel-rng.c b/drivers/char/hw_random/intel-rng.c
index cc1046e6ee02..4ae9811d1a6c 100644
--- a/drivers/char/hw_random/intel-rng.c
+++ b/drivers/char/hw_random/intel-rng.c
@@ -24,10 +24,11 @@
  * warranty of any kind, whether express or implied.
  */
 
-#include <linux/module.h>
+#include <linux/hw_random.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/pci.h>
-#include <linux/hw_random.h>
+#include <linux/stop_machine.h>
 #include <asm/io.h>
 
 
@@ -217,30 +218,117 @@ static struct hwrng intel_rng = {
         .data_read      = intel_rng_data_read,
 };
 
+struct intel_rng_hw {
+        struct pci_dev *dev;
+        void __iomem *mem;
+        u8 bios_cntl_off;
+        u8 bios_cntl_val;
+        u8 fwh_dec_en1_off;
+        u8 fwh_dec_en1_val;
+};
 
-#ifdef CONFIG_SMP
-static char __initdata waitflag;
+static int __init intel_rng_hw_init(void *_intel_rng_hw)
+{
+        struct intel_rng_hw *intel_rng_hw = _intel_rng_hw;
+        u8 mfc, dvc;
+
+        /* interrupts disabled in stop_machine_run call */
+
+        if (!(intel_rng_hw->fwh_dec_en1_val & FWH_F8_EN_MASK))
+                pci_write_config_byte(intel_rng_hw->dev,
+                                      intel_rng_hw->fwh_dec_en1_off,
+                                      intel_rng_hw->fwh_dec_en1_val |
+                                      FWH_F8_EN_MASK);
+        if (!(intel_rng_hw->bios_cntl_val & BIOS_CNTL_WRITE_ENABLE_MASK))
+                pci_write_config_byte(intel_rng_hw->dev,
+                                      intel_rng_hw->bios_cntl_off,
+                                      intel_rng_hw->bios_cntl_val |
+                                      BIOS_CNTL_WRITE_ENABLE_MASK);
+
+        writeb(INTEL_FWH_RESET_CMD, intel_rng_hw->mem);
+        writeb(INTEL_FWH_READ_ID_CMD, intel_rng_hw->mem);
+        mfc = readb(intel_rng_hw->mem + INTEL_FWH_MANUFACTURER_CODE_ADDRESS);
+        dvc = readb(intel_rng_hw->mem + INTEL_FWH_DEVICE_CODE_ADDRESS);
+        writeb(INTEL_FWH_RESET_CMD, intel_rng_hw->mem);
+
+        if (!(intel_rng_hw->bios_cntl_val &
+              (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK)))
+                pci_write_config_byte(intel_rng_hw->dev,
+                                      intel_rng_hw->bios_cntl_off,
+                                      intel_rng_hw->bios_cntl_val);
+        if (!(intel_rng_hw->fwh_dec_en1_val & FWH_F8_EN_MASK))
+                pci_write_config_byte(intel_rng_hw->dev,
+                                      intel_rng_hw->fwh_dec_en1_off,
+                                      intel_rng_hw->fwh_dec_en1_val);
 
-static void __init intel_init_wait(void *unused)
+        if (mfc != INTEL_FWH_MANUFACTURER_CODE ||
+            (dvc != INTEL_FWH_DEVICE_CODE_8M &&
+             dvc != INTEL_FWH_DEVICE_CODE_4M)) {
+                printk(KERN_ERR PFX "FWH not detected\n");
+                return -ENODEV;
+        }
+
+        return 0;
+}
+
+static int __init intel_init_hw_struct(struct intel_rng_hw *intel_rng_hw,
+                                        struct pci_dev *dev)
 {
-        while (waitflag)
-                cpu_relax();
+        intel_rng_hw->bios_cntl_val = 0xff;
+        intel_rng_hw->fwh_dec_en1_val = 0xff;
+        intel_rng_hw->dev = dev;
+
+        /* Check for Intel 82802 */
+        if (dev->device < 0x2640) {
+                intel_rng_hw->fwh_dec_en1_off = FWH_DEC_EN1_REG_OLD;
+                intel_rng_hw->bios_cntl_off = BIOS_CNTL_REG_OLD;
+        } else {
+                intel_rng_hw->fwh_dec_en1_off = FWH_DEC_EN1_REG_NEW;
+                intel_rng_hw->bios_cntl_off = BIOS_CNTL_REG_NEW;
+        }
+
+        pci_read_config_byte(dev, intel_rng_hw->fwh_dec_en1_off,
+                             &intel_rng_hw->fwh_dec_en1_val);
+        pci_read_config_byte(dev, intel_rng_hw->bios_cntl_off,
+                             &intel_rng_hw->bios_cntl_val);
+
+        if ((intel_rng_hw->bios_cntl_val &
+             (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK))
+            == BIOS_CNTL_LOCK_ENABLE_MASK) {
+                static __initdata /*const*/ char warning[] =
+                        KERN_WARNING PFX "Firmware space is locked read-only. "
+                        KERN_WARNING PFX "If you can't or\n don't want to "
+                        KERN_WARNING PFX "disable this in firmware setup, and "
+                        KERN_WARNING PFX "if\n you are certain that your "
+                        KERN_WARNING PFX "system has a functional\n RNG, try"
+                        KERN_WARNING PFX "using the 'no_fwh_detect' option.\n";
+
+                if (no_fwh_detect)
+                        return -ENODEV;
+                printk(warning);
+                return -EBUSY;
+        }
+
+        intel_rng_hw->mem = ioremap_nocache(INTEL_FWH_ADDR, INTEL_FWH_ADDR_LEN);
+        if (intel_rng_hw->mem == NULL)
+                return -EBUSY;
+
+        return 0;
 }
-#endif
+
 
 static int __init mod_init(void)
 {
         int err = -ENODEV;
-        unsigned i;
+        int i;
         struct pci_dev *dev = NULL;
-        void __iomem *mem;
-        unsigned long flags;
-        u8 bios_cntl_off, fwh_dec_en1_off;
-        u8 bios_cntl_val = 0xff, fwh_dec_en1_val = 0xff;
-        u8 hw_status, mfc, dvc;
+        void __iomem *mem = mem;
+        u8 hw_status;
+        struct intel_rng_hw *intel_rng_hw;
 
         for (i = 0; !dev && pci_tbl[i].vendor; ++i)
-                dev = pci_get_device(pci_tbl[i].vendor, pci_tbl[i].device, NULL);
+                dev = pci_get_device(pci_tbl[i].vendor, pci_tbl[i].device,
+                                     NULL);
 
         if (!dev)
                 goto out; /* Device not found. */
@@ -250,39 +338,18 @@ static int __init mod_init(void)
                 goto fwh_done;
         }
 
-        /* Check for Intel 82802 */
-        if (dev->device < 0x2640) {
-                fwh_dec_en1_off = FWH_DEC_EN1_REG_OLD;
-                bios_cntl_off = BIOS_CNTL_REG_OLD;
-        } else {
-                fwh_dec_en1_off = FWH_DEC_EN1_REG_NEW;
-                bios_cntl_off = BIOS_CNTL_REG_NEW;
-        }
-
-        pci_read_config_byte(dev, fwh_dec_en1_off, &fwh_dec_en1_val);
-        pci_read_config_byte(dev, bios_cntl_off, &bios_cntl_val);
-
-        if ((bios_cntl_val &
-             (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK))
-            == BIOS_CNTL_LOCK_ENABLE_MASK) {
-                static __initdata /*const*/ char warning[] =
-                        KERN_WARNING PFX "Firmware space is locked read-only. If you can't or\n"
-                        KERN_WARNING PFX "don't want to disable this in firmware setup, and if\n"
-                        KERN_WARNING PFX "you are certain that your system has a functional\n"
-                        KERN_WARNING PFX "RNG, try using the 'no_fwh_detect' option.\n";
-
+        intel_rng_hw = kmalloc(sizeof(*intel_rng_hw), GFP_KERNEL);
+        if (!intel_rng_hw) {
                 pci_dev_put(dev);
-                if (no_fwh_detect)
-                        goto fwh_done;
-                printk(warning);
-                err = -EBUSY;
                 goto out;
         }
 
-        mem = ioremap_nocache(INTEL_FWH_ADDR, INTEL_FWH_ADDR_LEN);
-        if (mem == NULL) {
+        err = intel_init_hw_struct(intel_rng_hw, dev);
+        if (err) {
                 pci_dev_put(dev);
-                err = -EBUSY;
+                kfree(intel_rng_hw);
+                if (err == -ENODEV)
+                        goto fwh_done;
                 goto out;
         }
 
@@ -290,59 +357,18 @@ static int __init mod_init(void)
          * Since the BIOS code/data is going to disappear from its normal
          * location with the Read ID command, all activity on the system
          * must be stopped until the state is back to normal.
+         *
+         * Use stop_machine_run because IPIs can be blocked by disabling
+         * interrupts.
          */
-#ifdef CONFIG_SMP
-        set_mb(waitflag, 1);
-        if (smp_call_function(intel_init_wait, NULL, 1, 0) != 0) {
-                set_mb(waitflag, 0);
-                pci_dev_put(dev);
-                printk(KERN_ERR PFX "cannot run on all processors\n");
-                err = -EAGAIN;
-                goto err_unmap;
-        }
-#endif
-        local_irq_save(flags);
-
-        if (!(fwh_dec_en1_val & FWH_F8_EN_MASK))
-                pci_write_config_byte(dev,
-                                      fwh_dec_en1_off,
-                                      fwh_dec_en1_val | FWH_F8_EN_MASK);
-        if (!(bios_cntl_val & BIOS_CNTL_WRITE_ENABLE_MASK))
-                pci_write_config_byte(dev,
-                                      bios_cntl_off,
-                                      bios_cntl_val | BIOS_CNTL_WRITE_ENABLE_MASK);
-
-        writeb(INTEL_FWH_RESET_CMD, mem);
-        writeb(INTEL_FWH_READ_ID_CMD, mem);
-        mfc = readb(mem + INTEL_FWH_MANUFACTURER_CODE_ADDRESS);
-        dvc = readb(mem + INTEL_FWH_DEVICE_CODE_ADDRESS);
-        writeb(INTEL_FWH_RESET_CMD, mem);
-
-        if (!(bios_cntl_val &
-              (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK)))
-                pci_write_config_byte(dev, bios_cntl_off, bios_cntl_val);
-        if (!(fwh_dec_en1_val & FWH_F8_EN_MASK))
-                pci_write_config_byte(dev, fwh_dec_en1_off, fwh_dec_en1_val);
-
-        local_irq_restore(flags);
-#ifdef CONFIG_SMP
-        /* Tell other CPUs to resume. */
-        set_mb(waitflag, 0);
-#endif
-
-        iounmap(mem);
+        err = stop_machine_run(intel_rng_hw_init, intel_rng_hw, NR_CPUS);
         pci_dev_put(dev);
-
-        if (mfc != INTEL_FWH_MANUFACTURER_CODE ||
-            (dvc != INTEL_FWH_DEVICE_CODE_8M &&
-             dvc != INTEL_FWH_DEVICE_CODE_4M)) {
-                printk(KERN_ERR PFX "FWH not detected\n");
-                err = -ENODEV;
+        iounmap(intel_rng_hw->mem);
+        kfree(intel_rng_hw);
+        if (err)
                 goto out;
-        }
 
 fwh_done:
-
         err = -ENOMEM;
         mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
         if (!mem)
@@ -352,22 +378,21 @@ fwh_done:
         /* Check for Random Number Generator */
         err = -ENODEV;
         hw_status = hwstatus_get(mem);
-        if ((hw_status & INTEL_RNG_PRESENT) == 0)
-                goto err_unmap;
+        if ((hw_status & INTEL_RNG_PRESENT) == 0) {
+                iounmap(mem);
+                goto out;
+        }
 
         printk(KERN_INFO "Intel 82802 RNG detected\n");
         err = hwrng_register(&intel_rng);
         if (err) {
                 printk(KERN_ERR PFX "RNG registering failed (%d)\n",
                        err);
-                goto err_unmap;
+                iounmap(mem);
         }
 out:
         return err;
 
-err_unmap:
-        iounmap(mem);
-        goto out;
 }
 
 static void __exit mod_exit(void)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 12458040e665..daabb74ee0bc 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -1,11 +1,12 @@
 /* Copyright 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation.
  * GPL v2 and any later version.
  */
-#include <linux/stop_machine.h>
-#include <linux/kthread.h>
-#include <linux/sched.h>
 #include <linux/cpu.h>
 #include <linux/err.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/stop_machine.h>
 #include <linux/syscalls.h>
 #include <asm/atomic.h>
 #include <asm/semaphore.h>
@@ -208,3 +209,4 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
 
         return ret;
 }
+EXPORT_SYMBOL_GPL(stop_machine_run);