[Xen-devel] [PATCH 6/6] MCE: Be more careful for printk in MCE context

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Be more careful for printk in MCE context

MCE may happen in printk context, and will cause deadlock if we try to call 
printk again in MCE context.

A new level(mce_critical) is added to mce_verbosity for printk in mce context. 
This level is only for developer that aware of such issue.
In mce_panic, force console unlock.

Singed-off-by: Jiang, Yunhong <yunhong.jiang@xxxxxxxxx>

diff -r 9b31dd6deff7 xen/arch/x86/cpu/mcheck/mce.c
--- a/xen/arch/x86/cpu/mcheck/mce.c     Wed Jan 27 20:39:09 2010 +0800
+++ b/xen/arch/x86/cpu/mcheck/mce.c     Wed Jan 27 20:39:19 2010 +0800
@@ -1606,7 +1606,7 @@ void mc_panic(char *s)
 void mc_panic(char *s)
 {
     is_mc_panic = 1;
-    console_start_sync();
+    console_force_unlock();
     printk("Fatal machine check: %s\n", s);
     printk("\n"
            "****************************************\n"
diff -r 9b31dd6deff7 xen/arch/x86/cpu/mcheck/mce.h
--- a/xen/arch/x86/cpu/mcheck/mce.h     Wed Jan 27 20:39:09 2010 +0800
+++ b/xen/arch/x86/cpu/mcheck/mce.h     Wed Jan 27 20:39:19 2010 +0800
@@ -12,8 +12,10 @@
 #include "x86_mca.h"
 #include "mctelem.h"
 
-#define MCE_QUIET 0
-#define MCE_VERBOSE 1
+#define MCE_QUIET       0
+#define MCE_VERBOSE     1
+/* !only for developer debug as printk is unsafe in MCE context */
+#define MCE_CRITICAL    2
 
 extern int mce_verbosity;
 /* Define the default level of machine check related print.
diff -r 9b31dd6deff7 xen/arch/x86/cpu/mcheck/mce_intel.c
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c       Wed Jan 27 20:39:09 2010 +0800
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c       Wed Jan 27 20:39:19 2010 +0800
@@ -687,7 +687,7 @@ static void intel_machine_check(struct c
         }
         atomic_set(&found_error, 1);
 
-        mce_printk(MCE_VERBOSE, "MCE: clear_bank map %lx on CPU%d\n",
+        mce_printk(MCE_CRITICAL, "MCE: clear_bank map %lx on CPU%d\n",
                 *((unsigned long*)clear_bank), smp_processor_id());
         mcheck_mca_clearbanks(clear_bank);
        /* Print MCE error */
@@ -714,13 +714,13 @@ static void intel_machine_check(struct c
     /* Clear error finding flags after all cpus finishes above judgement */
     mce_barrier_enter(&mce_trap_bar);
     if (atomic_read(&found_error)) {
-        mce_printk(MCE_VERBOSE, "MCE: Choose one CPU "
+        mce_printk(MCE_CRITICAL, "MCE: Choose one CPU "
                        "to clear error finding flag\n ");
         atomic_set(&found_error, 0);
     }
     mca_rdmsrl(MSR_IA32_MCG_STATUS, gstatus);
     if ((gstatus & MCG_STATUS_MCIP) != 0) {
-        mce_printk(MCE_VERBOSE, "MCE: Clear MCIP@ last step");
+        mce_printk(MCE_CRITICAL, "MCE: Clear MCIP@ last step");
         mca_wrmsrl(MSR_IA32_MCG_STATUS, gstatus & ~MCG_STATUS_MCIP);
     }
     mce_barrier_exit(&mce_trap_bar);

Attachment: mce_printk.patch
Description: mce_printk.patch

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