[PATCH] reduce side effects of handling '*' debug key

["Jan Beulich" <JBeulich@novell.com>]

[-- Attachment #1: Type: text/plain, Size: 1803 bytes --]

NMI watchdog should be suppressed, and softirqs should be handled at
least in the non-IRQ handler portion (they obviously must not be
processed in IRQ context).

The (slightly more involved) 4.0 variant of this patch is also
attached.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -444,16 +444,21 @@ static void run_all_nonirq_keyhandlers(u
     struct keyhandler *h;
     int k;
 
-    console_start_log_everything();
+    watchdog_disable();
+    console_start_sync();
+
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
+        process_pending_softirqs();
         h = key_table[k];
         if ( (h == NULL) || !h->diagnostic || h->irq_callback )
             continue;
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.fn)(k);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 }
 
 static DECLARE_TASKLET(run_all_keyhandlers_tasklet,
@@ -464,10 +469,12 @@ static void run_all_keyhandlers(unsigned
     struct keyhandler *h;
     int k;
 
+    watchdog_disable();
+    console_start_sync();
+
     printk("'%c' pressed -> firing all diagnostic keyhandlers\n", key);
 
     /* Fire all the IRQ-context diangostic keyhandlers now */
-    console_start_log_everything();
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
         h = key_table[k];
@@ -476,7 +483,9 @@ static void run_all_keyhandlers(unsigned
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.irq_fn)(k, regs);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 
     /* Trigger the others from a tasklet in non-IRQ context */
     tasklet_schedule(&run_all_keyhandlers_tasklet);




[-- Attachment #2: keyhandler-relax.patch --]
[-- Type: text/plain, Size: 1797 bytes --]

NMI watchdog should be suppressed, and softirqs should be handled at
least in the non-IRQ handler portion (they obviously must not be
processed in IRQ context).

The (slightly more involved) 4.0 variant of this patch is also
attached.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -444,16 +444,21 @@ static void run_all_nonirq_keyhandlers(u
     struct keyhandler *h;
     int k;
 
-    console_start_log_everything();
+    watchdog_disable();
+    console_start_sync();
+
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
+        process_pending_softirqs();
         h = key_table[k];
         if ( (h == NULL) || !h->diagnostic || h->irq_callback )
             continue;
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.fn)(k);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 }
 
 static DECLARE_TASKLET(run_all_keyhandlers_tasklet,
@@ -464,10 +469,12 @@ static void run_all_keyhandlers(unsigned
     struct keyhandler *h;
     int k;
 
+    watchdog_disable();
+    console_start_sync();
+
     printk("'%c' pressed -> firing all diagnostic keyhandlers\n", key);
 
     /* Fire all the IRQ-context diangostic keyhandlers now */
-    console_start_log_everything();
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
         h = key_table[k];
@@ -476,7 +483,9 @@ static void run_all_keyhandlers(unsigned
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.irq_fn)(k, regs);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 
     /* Trigger the others from a tasklet in non-IRQ context */
     tasklet_schedule(&run_all_keyhandlers_tasklet);

[-- Attachment #3: 4.0-keyhandler-relax.patch --]
[-- Type: text/plain, Size: 2889 bytes --]

NMI watchdog should be suppressed, and softirqs should be handled at
least in the non-IRQ handler portion (they obviously must not be
processed in IRQ context). Since softirqs, other than in 4.1, get
handled in a tasklet, we need to make sure we don't nest softirq
execution, which requires a new clone of process_pending_softirqs().

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -375,16 +375,21 @@ static void run_all_nonirq_keyhandlers(u
     struct keyhandler *h;
     int k;
 
-    console_start_log_everything();
+    watchdog_disable();
+    console_start_sync();
+
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
+        process_pending_softirqs_nested();
         h = key_table[k];
         if ( (h == NULL) || !h->diagnostic || h->irq_callback )
             continue;
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.fn)(k);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 }
 
 static DECLARE_TASKLET(run_all_keyhandlers_tasklet,
@@ -395,10 +400,12 @@ static void run_all_keyhandlers(unsigned
     struct keyhandler *h;
     int k;
 
+    watchdog_disable();
+    console_start_sync();
+
     printk("'%c' pressed -> firing all diagnostic keyhandlers\n", key);
 
     /* Fire all the IRQ-context diangostic keyhandlers now */
-    console_start_log_everything();
     for ( k = 0; k < ARRAY_SIZE(key_table); k++ )
     {
         h = key_table[k];
@@ -407,7 +414,9 @@ static void run_all_keyhandlers(unsigned
         printk("[%c: %s]\n", k, h->desc);
         (*h->u.irq_fn)(k, regs);
     }
-    console_end_log_everything();
+
+    console_end_sync();
+    watchdog_enable();
 
     /* Trigger the others from a tasklet in non-IRQ context */
     tasklet_schedule(&run_all_keyhandlers_tasklet);
--- a/xen/common/softirq.c
+++ b/xen/common/softirq.c
@@ -54,6 +54,16 @@ void process_pending_softirqs(void)
     __do_softirq(1ul<<SCHEDULE_SOFTIRQ);
 }
 
+void process_pending_softirqs_nested(void)
+{
+    ASSERT(!in_irq() && local_irq_is_enabled());
+    /*
+     * Do not enter scheduler as it can preempt the calling context,
+     * and do not run tasklets as we're running one currently.
+     */
+    __do_softirq((1ul<<SCHEDULE_SOFTIRQ) | (1ul<<TASKLET_SOFTIRQ));
+}
+
 asmlinkage void do_softirq(void)
 {
     __do_softirq(0);
--- a/xen/include/xen/softirq.h
+++ b/xen/include/xen/softirq.h
@@ -39,6 +39,8 @@ void raise_softirq(unsigned int nr);
  * Use this instead of do_softirq() when you do not want to be preempted.
  */
 void process_pending_softirqs(void);
+/* ... and use this instead when running inside a tasklet. */
+void process_pending_softirqs_nested(void);
 
 /*
  * TASKLETS -- dynamically-allocatable tasks run in softirq context

[-- Attachment #4: Type: text/plain, Size: 138 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel