6 files changed, 69 insertions, 21 deletions

diff --git a/Documentation/workqueue.txt b/Documentation/workqueue.txt
index 01c513fac40e..a0b577de918f 100644
--- a/Documentation/workqueue.txt
+++ b/Documentation/workqueue.txt
@@ -12,6 +12,7 @@ CONTENTS
 4. Application Programming Interface (API)
 5. Example Execution Scenarios
 6. Guidelines
+7. Debugging
 
 
 1. Introduction
@@ -379,3 +380,42 @@ If q1 has WQ_CPU_INTENSIVE set,
 * Unless work items are expected to consume a huge amount of CPU
   cycles, using a bound wq is usually beneficial due to the increased
   level of locality in wq operations and work item execution.
+
+
+7. Debugging
+
+Because the work functions are executed by generic worker threads
+there are a few tricks needed to shed some light on misbehaving
+workqueue users.
+
+Worker threads show up in the process list as:
+
+root      5671  0.0  0.0      0     0 ?        S    12:07   0:00 [kworker/0:1]
+root      5672  0.0  0.0      0     0 ?        S    12:07   0:00 [kworker/1:2]
+root      5673  0.0  0.0      0     0 ?        S    12:12   0:00 [kworker/0:0]
+root      5674  0.0  0.0      0     0 ?        S    12:13   0:00 [kworker/1:0]
+
+If kworkers are going crazy (using too much cpu), there are two types
+of possible problems:
+
+        1. Something beeing scheduled in rapid succession
+        2. A single work item that consumes lots of cpu cycles
+
+The first one can be tracked using tracing:
+
+        $ echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event
+        $ cat /sys/kernel/debug/tracing/trace_pipe > out.txt
+        (wait a few secs)
+        ^C
+
+If something is busy looping on work queueing, it would be dominating
+the output and the offender can be determined with the work item
+function.
+
+For the second type of problems it should be possible to just check
+the stack trace of the offending worker thread.
+
+        $ cat /proc/THE_OFFENDING_KWORKER/stack
+
+The work item's function should be trivially visible in the stack
+trace.
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 72c0415f6f94..455e909bc768 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -134,10 +134,15 @@
                                  SMBHSTSTS_BUS_ERR | SMBHSTSTS_DEV_ERR | \
                                  SMBHSTSTS_INTR)
 
+/* Older devices have their ID defined in <linux/pci_ids.h> */
+#define PCI_DEVICE_ID_INTEL_COUGARPOINT_SMBUS   0x1c22
+#define PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS      0x1d22
 /* Patsburg also has three 'Integrated Device Function' SMBus controllers */
 #define PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS_IDF0 0x1d70
 #define PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS_IDF1 0x1d71
 #define PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS_IDF2 0x1d72
+#define PCI_DEVICE_ID_INTEL_DH89XXCC_SMBUS      0x2330
+#define PCI_DEVICE_ID_INTEL_5_3400_SERIES_SMBUS 0x3b30
 
 struct i801_priv {
         struct i2c_adapter adapter;
diff --git a/drivers/i2c/busses/i2c-parport.c b/drivers/i2c/busses/i2c-parport.c
index 0eb1515541e7..2dbba163b102 100644
--- a/drivers/i2c/busses/i2c-parport.c
+++ b/drivers/i2c/busses/i2c-parport.c
@@ -1,7 +1,7 @@
 /* ------------------------------------------------------------------------ *
  * i2c-parport.c I2C bus over parallel port                                 *
  * ------------------------------------------------------------------------ *
-   Copyright (C) 2003-2010 Jean Delvare <khali@linux-fr.org>
+   Copyright (C) 2003-2011 Jean Delvare <khali@linux-fr.org>
    
    Based on older i2c-philips-par.c driver
    Copyright (C) 1995-2000 Simon G. Vogl
@@ -33,6 +33,8 @@
 #include <linux/i2c-algo-bit.h>
 #include <linux/i2c-smbus.h>
 #include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
 #include "i2c-parport.h"
 
 /* ----- Device list ------------------------------------------------------ */
@@ -43,10 +45,11 @@ struct i2c_par {
         struct i2c_algo_bit_data algo_data;
         struct i2c_smbus_alert_setup alert_data;
         struct i2c_client *ara;
-        struct i2c_par *next;
+        struct list_head node;
 };
 
-static struct i2c_par *adapter_list;
+static LIST_HEAD(adapter_list);
+static DEFINE_MUTEX(adapter_list_lock);
 
 /* ----- Low-level parallel port access ----------------------------------- */
 
@@ -228,8 +231,9 @@ static void i2c_parport_attach (struct parport *port)
         }
 
         /* Add the new adapter to the list */
-        adapter->next = adapter_list;
-        adapter_list = adapter;
+        mutex_lock(&adapter_list_lock);
+        list_add_tail(&adapter->node, &adapter_list);
+        mutex_unlock(&adapter_list_lock);
         return;
 
 ERROR1:
@@ -241,11 +245,11 @@ ERROR0:
 
 static void i2c_parport_detach (struct parport *port)
 {
-        struct i2c_par *adapter, *prev;
+        struct i2c_par *adapter, *_n;
 
         /* Walk the list */
-        for (prev = NULL, adapter = adapter_list; adapter;
-             prev = adapter, adapter = adapter->next) {
+        mutex_lock(&adapter_list_lock);
+        list_for_each_entry_safe(adapter, _n, &adapter_list, node) {
                 if (adapter->pdev->port == port) {
                         if (adapter->ara) {
                                 parport_disable_irq(port);
@@ -259,14 +263,11 @@ static void i2c_parport_detach (struct parport *port)
                                 
                         parport_release(adapter->pdev);
                         parport_unregister_device(adapter->pdev);
-                        if (prev)
-                                prev->next = adapter->next;
-                        else
-                                adapter_list = adapter->next;
+                        list_del(&adapter->node);
                         kfree(adapter);
-                        return;
                 }
         }
+        mutex_unlock(&adapter_list_lock);
 }
 
 static struct parport_driver i2c_parport_driver = {
diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
index 4e2c9150a785..8abe8d78c4bf 100644
--- a/include/linux/pci_ids.h
+++ b/include/linux/pci_ids.h
@@ -2477,15 +2477,12 @@
 #define PCI_DEVICE_ID_INTEL_82840_HB    0x1a21
 #define PCI_DEVICE_ID_INTEL_82845_HB    0x1a30
 #define PCI_DEVICE_ID_INTEL_IOAT        0x1a38
-#define PCI_DEVICE_ID_INTEL_COUGARPOINT_SMBUS   0x1c22
 #define PCI_DEVICE_ID_INTEL_COUGARPOINT_LPC_MIN 0x1c41
 #define PCI_DEVICE_ID_INTEL_COUGARPOINT_LPC_MAX 0x1c5f
-#define PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS      0x1d22
 #define PCI_DEVICE_ID_INTEL_PATSBURG_LPC_0      0x1d40
 #define PCI_DEVICE_ID_INTEL_PATSBURG_LPC_1      0x1d41
 #define PCI_DEVICE_ID_INTEL_DH89XXCC_LPC_MIN    0x2310
 #define PCI_DEVICE_ID_INTEL_DH89XXCC_LPC_MAX    0x231f
-#define PCI_DEVICE_ID_INTEL_DH89XXCC_SMBUS      0x2330
 #define PCI_DEVICE_ID_INTEL_82801AA_0   0x2410
 #define PCI_DEVICE_ID_INTEL_82801AA_1   0x2411
 #define PCI_DEVICE_ID_INTEL_82801AA_3   0x2413
@@ -2696,7 +2693,6 @@
 #define PCI_DEVICE_ID_INTEL_ICH10_5     0x3a60
 #define PCI_DEVICE_ID_INTEL_5_3400_SERIES_LPC_MIN       0x3b00
 #define PCI_DEVICE_ID_INTEL_5_3400_SERIES_LPC_MAX       0x3b1f
-#define PCI_DEVICE_ID_INTEL_5_3400_SERIES_SMBUS 0x3b30
 #define PCI_DEVICE_ID_INTEL_IOAT_SNB    0x402f
 #define PCI_DEVICE_ID_INTEL_5100_16     0x65f0
 #define PCI_DEVICE_ID_INTEL_5100_21     0x65f5
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 8859a41806dd..e3378e8d3a5c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1291,8 +1291,14 @@ __acquires(&gcwq->lock)
                         return true;
                 spin_unlock_irq(&gcwq->lock);
 
-                /* CPU has come up in between, retry migration */
+                /*
+                 * We've raced with CPU hot[un]plug.  Give it a breather
+                 * and retry migration.  cond_resched() is required here;
+                 * otherwise, we might deadlock against cpu_stop trying to
+                 * bring down the CPU on non-preemptive kernel.
+                 */
                 cpu_relax();
+                cond_resched();
         }
 }
 
diff --git a/lib/xz/xz_dec_lzma2.c b/lib/xz/xz_dec_lzma2.c
index ea5fa4fe9d67..a6cdc969ea42 100644
--- a/lib/xz/xz_dec_lzma2.c
+++ b/lib/xz/xz_dec_lzma2.c
@@ -969,6 +969,9 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
                          */
                         tmp = b->in[b->in_pos++];
 
+                        if (tmp == 0x00)
+                                return XZ_STREAM_END;
+
                         if (tmp >= 0xE0 || tmp == 0x01) {
                                 s->lzma2.need_props = true;
                                 s->lzma2.need_dict_reset = false;
@@ -1001,9 +1004,6 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
                                                 lzma_reset(s);
                                 }
                         } else {
-                                if (tmp == 0x00)
-                                        return XZ_STREAM_END;
-
                                 if (tmp > 0x02)
                                         return XZ_DATA_ERROR;