[Xen-changelog] [xen master] keyhandler: rework process of nonirq keyhandler

[patchbot@xxxxxxx]

commit 610b4eda2ce2b87cccbc8f61bdec01052e54fc66
Author:     Lan Tianyu <tianyu.lan@xxxxxxxxx>
AuthorDate: Thu Oct 13 13:06:28 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 13 13:06:28 2016 +0200

    keyhandler: rework process of nonirq keyhandler
    
    Keyhandler may run for a long time in serial port driver's
    timer handler on the large machine with a lot of physical
    cpus(e,g dump_timerq()) when serial port driver works in
    the poll mode(via the exception mechanism).
    
    If a timer handler runs a long time, it will block nmi_timer_fn()
    to feed NMI watchdog and cause Xen hypervisor panic. Inserting
    process_pending_softirqs() in timer handler will not help. when timer
    interrupt arrives, timer subsystem calls all expired timer handlers
    before programming next timer interrupt. There is no timer interrupt
    arriving to trigger timer softirq during run a timer handler.
    
    This patch is to fix the issue to make nonirq keyhandler run in
    tasklet when receive debug key from serial port.
    
    Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/keyhandler.c      | 9 ++++++---
 xen/common/sysctl.c          | 2 +-
 xen/drivers/char/console.c   | 2 +-
 xen/include/xen/keyhandler.h | 3 ++-
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
index 16de6e8..2f7c364 100644
--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -75,19 +75,22 @@ static struct keyhandler {
 
 static void keypress_action(unsigned long unused)
 {
-    handle_keypress(keypress_key, NULL);
+    console_start_log_everything();
+    key_table[keypress_key].fn(keypress_key);
+    console_end_log_everything();
 }
 
 static DECLARE_TASKLET(keypress_tasklet, keypress_action, 0);
 
-void handle_keypress(unsigned char key, struct cpu_user_regs *regs)
+void handle_keypress(unsigned char key, struct cpu_user_regs *regs,
+                     bool force_tasklet)
 {
     struct keyhandler *h;
 
     if ( key >= ARRAY_SIZE(key_table) || !(h = &key_table[key])->fn )
         return;
 
-    if ( !in_irq() || h->irq_callback )
+    if ( h->irq_callback || !force_tasklet )
     {
         console_start_log_everything();
         h->irq_callback ? h->irq_fn(key, regs) : h->fn(key);
diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index 8aea6ef..1eb7bad 100644
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -136,7 +136,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) 
u_sysctl)
         {
             if ( copy_from_guest_offset(&c, op->u.debug_keys.keys, i, 1) )
                 goto out;
-            handle_keypress(c, guest_cpu_user_regs());
+            handle_keypress(c, guest_cpu_user_regs(), false);
         }
         ret = 0;
         copyback = 0;
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 55ae31a..b0f74ce 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -347,7 +347,7 @@ static void switch_serial_input(void)
 static void __serial_rx(char c, struct cpu_user_regs *regs)
 {
     if ( xen_rx )
-        return handle_keypress(c, regs);
+        return handle_keypress(c, regs, !in_irq());
 
     /* Deliver input to guest buffer, unless it is already full. */
     if ( (serial_rx_prod-serial_rx_cons) != SERIAL_RX_SIZE )
diff --git a/xen/include/xen/keyhandler.h b/xen/include/xen/keyhandler.h
index 06c05c8..fe32d8a 100644
--- a/xen/include/xen/keyhandler.h
+++ b/xen/include/xen/keyhandler.h
@@ -46,7 +46,8 @@ void register_irq_keyhandler(unsigned char key,
                              bool_t diagnostic);
 
 /* Inject a keypress into the key-handling subsystem. */
-extern void handle_keypress(unsigned char key, struct cpu_user_regs *regs);
+extern void handle_keypress(unsigned char key, struct cpu_user_regs *regs,
+                            bool force_tasklet);
 
 /* Scratch space is available for use of any keyhandler. */
 extern char keyhandler_scratch[1024];
--
generated by git-patchbot for /home/xen/git/xen.git#master

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