5 files changed, 82 insertions, 40 deletions

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index a67f87bf401..830cfc6ee8c 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -282,7 +282,7 @@ sysret_careful:
 sysret_signal:
         TRACE_IRQS_ON
         sti
-        testl $(_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SINGLESTEP),%edx
+        testl $(_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx
         jz    1f
 
         /* Really a signal */
@@ -375,7 +375,7 @@ int_very_careful:
         jmp int_restore_rest
         
 int_signal:
-        testl $(_TIF_NOTIFY_RESUME|_TIF_SIGPENDING|_TIF_SINGLESTEP),%edx
+        testl $(_TIF_NOTIFY_RESUME|_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx
         jz 1f
         movq %rsp,%rdi          # &ptregs -> arg1
         xorl %esi,%esi          # oldset -> arg2
@@ -599,7 +599,7 @@ retint_careful:
         jmp retint_check
         
 retint_signal:
-        testl $(_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SINGLESTEP),%edx
+        testl $(_TIF_SIGPENDING|_TIF_NOTIFY_RESUME|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx
         jz    retint_swapgs
         TRACE_IRQS_ON
         sti
diff --git a/arch/x86_64/kernel/mce.c b/arch/x86_64/kernel/mce.c
index 77fee481be4..968613572b9 100644
--- a/arch/x86_64/kernel/mce.c
+++ b/arch/x86_64/kernel/mce.c
@@ -18,6 +18,8 @@
 #include <linux/capability.h>
 #include <linux/cpu.h>
 #include <linux/percpu.h>
+#include <linux/poll.h>
+#include <linux/thread_info.h>
 #include <linux/ctype.h>
 #include <linux/kmod.h>
 #include <linux/kdebug.h>
@@ -26,6 +28,7 @@
 #include <asm/mce.h>
 #include <asm/uaccess.h>
 #include <asm/smp.h>
+#include <asm/idle.h>
 
 #define MISC_MCELOG_MINOR 227
 #define NR_BANKS 6
@@ -39,8 +42,7 @@ static int mce_dont_init;
 static int tolerant = 1;
 static int banks;
 static unsigned long bank[NR_BANKS] = { [0 ... NR_BANKS-1] = ~0UL };
-static unsigned long console_logged;
-static int notify_user;
+static unsigned long notify_user;
 static int rip_msr;
 static int mce_bootlog = 1;
 static atomic_t mce_events;
@@ -48,6 +50,8 @@ static atomic_t mce_events;
 static char trigger[128];
 static char *trigger_argv[2] = { trigger, NULL };
 
+static DECLARE_WAIT_QUEUE_HEAD(mce_wait);
+
 /*
  * Lockless MCE logging infrastructure.
  * This avoids deadlocks on printk locks without having to break locks. Also
@@ -94,8 +98,7 @@ void mce_log(struct mce *mce)
         mcelog.entry[entry].finished = 1;
         wmb();
 
-        if (!test_and_set_bit(0, &console_logged))
-                notify_user = 1;
+        set_bit(0, &notify_user);
 }
 
 static void print_mce(struct mce *m)
@@ -128,6 +131,10 @@ static void print_mce(struct mce *m)
 static void mce_panic(char *msg, struct mce *backup, unsigned long start)
 { 
         int i;
+
+        if (tolerant >= 3)
+                return;
+
         oops_begin();
         for (i = 0; i < MCE_LOG_LEN; i++) {
                 unsigned long tsc = mcelog.entry[i].tsc;
@@ -139,10 +146,7 @@ static void mce_panic(char *msg, struct mce *backup, unsigned long start)
         }
         if (backup)
                 print_mce(backup);
-        if (tolerant >= 3)
-                printk("Fake panic: %s\n", msg);
-        else
-                panic(msg);
+        panic(msg);
 } 
 
 static int mce_available(struct cpuinfo_x86 *c)
@@ -167,17 +171,6 @@ static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
         }
 }
 
-static void do_mce_trigger(void)
-{
-        static atomic_t mce_logged;
-        int events = atomic_read(&mce_events);
-        if (events != atomic_read(&mce_logged) && trigger[0]) {
-                /* Small race window, but should be harmless.  */
-                atomic_set(&mce_logged, events);
-                call_usermodehelper(trigger, trigger_argv, NULL, UMH_NO_WAIT);
-        }
-}
-
 /* 
  * The actual machine check handler
  */
@@ -251,12 +244,8 @@ void do_machine_check(struct pt_regs * regs, long error_code)
         }
 
         /* Never do anything final in the polling timer */
-        if (!regs) {
-                /* Normal interrupt context here. Call trigger for any new
-                   events. */
-                do_mce_trigger();
+        if (!regs)
                 goto out;
-        }
 
         /* If we didn't find an uncorrectable error, pick
            the last one (shouldn't happen, just being safe). */
@@ -288,6 +277,9 @@ void do_machine_check(struct pt_regs * regs, long error_code)
                         do_exit(SIGBUS);
         }
 
+        /* notify userspace ASAP */
+        set_thread_flag(TIF_MCE_NOTIFY);
+
  out:
         /* Last thing done in the machine check exception to clear state. */
         wrmsrl(MSR_IA32_MCG_STATUS, 0);
@@ -344,37 +336,67 @@ static void mcheck_timer(struct work_struct *work)
         on_each_cpu(mcheck_check_cpu, NULL, 1, 1);
 
         /*
-         * It's ok to read stale data here for notify_user and
-         * console_logged as we'll simply get the updated versions
-         * on the next mcheck_timer execution and atomic operations
-         * on console_logged act as synchronization for notify_user
-         * writes.
+         * Alert userspace if needed.  If we logged an MCE, reduce the
+         * polling interval, otherwise increase the polling interval.
          */
-        if (notify_user && console_logged) {
+        if (mce_notify_user()) {
+                next_interval = max(next_interval/2, HZ/100);
+        } else {
+                next_interval = min(next_interval*2, check_interval*HZ);
+        }
+
+        schedule_delayed_work(&mcheck_work, next_interval);
+}
+
+/*
+ * This is only called from process context.  This is where we do
+ * anything we need to alert userspace about new MCEs.  This is called
+ * directly from the poller and also from entry.S and idle, thanks to
+ * TIF_MCE_NOTIFY.
+ */
+int mce_notify_user(void)
+{
+        clear_thread_flag(TIF_MCE_NOTIFY);
+        if (test_and_clear_bit(0, &notify_user)) {
                 static unsigned long last_print;
                 unsigned long now = jiffies;
 
-                /* if we logged an MCE, reduce the polling interval */
-                next_interval = max(next_interval/2, HZ/100);
-                notify_user = 0;
-                clear_bit(0, &console_logged);
+                wake_up_interruptible(&mce_wait);
+                if (trigger[0])
+                        call_usermodehelper(trigger, trigger_argv, NULL,
+                                                UMH_NO_WAIT);
+
                 if (time_after_eq(now, last_print + (check_interval*HZ))) {
                         last_print = now;
                         printk(KERN_INFO "Machine check events logged\n");
                 }
-        } else {
-                next_interval = min(next_interval*2, check_interval*HZ);
+
+                return 1;
         }
+        return 0;
+}
 
-        schedule_delayed_work(&mcheck_work, next_interval);
+/* see if the idle task needs to notify userspace */
+static int
+mce_idle_callback(struct notifier_block *nfb, unsigned long action, void *junk)
+{
+        /* IDLE_END should be safe - interrupts are back on */
+        if (action == IDLE_END && test_thread_flag(TIF_MCE_NOTIFY))
+                mce_notify_user();
+
+        return NOTIFY_OK;
 }
 
+static struct notifier_block mce_idle_notifier = {
+        .notifier_call = mce_idle_callback,
+};
 
 static __init int periodic_mcheck_init(void)
 { 
         next_interval = check_interval * HZ;
         if (next_interval)
                 schedule_delayed_work(&mcheck_work, next_interval);
+        idle_notifier_register(&mce_idle_notifier);
         return 0;
 } 
 __initcall(periodic_mcheck_init);
@@ -566,6 +588,14 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize, loff
         return err ? -EFAULT : buf - ubuf; 
 }
 
+static unsigned int mce_poll(struct file *file, poll_table *wait)
+{
+        poll_wait(file, &mce_wait, wait);
+        if (rcu_dereference(mcelog.next))
+                return POLLIN | POLLRDNORM;
+        return 0;
+}
+
 static int mce_ioctl(struct inode *i, struct file *f,unsigned int cmd, unsigned long arg)
 {
         int __user *p = (int __user *)arg;
@@ -592,6 +622,7 @@ static const struct file_operations mce_chrdev_ops = {
         .open = mce_open,
         .release = mce_release,
         .read = mce_read,
+        .poll = mce_poll,
         .ioctl = mce_ioctl,
 };
 
diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c
index 290f5d8037c..4886afcd628 100644
--- a/arch/x86_64/kernel/signal.c
+++ b/arch/x86_64/kernel/signal.c
@@ -26,6 +26,7 @@
 #include <asm/i387.h>
 #include <asm/proto.h>
 #include <asm/ia32_unistd.h>
+#include <asm/mce.h>
 
 /* #define DEBUG_SIG 1 */
 
@@ -472,6 +473,12 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
                 clear_thread_flag(TIF_SINGLESTEP);
         }
 
+#ifdef CONFIG_X86_MCE
+        /* notify userspace of pending MCEs */
+        if (thread_info_flags & _TIF_MCE_NOTIFY)
+                mce_notify_user();
+#endif /* CONFIG_X86_MCE */
+
         /* deal with pending signal delivery */
         if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
                 do_signal(regs);
diff --git a/include/asm-x86_64/mce.h b/include/asm-x86_64/mce.h
index 177e92b4019..556be5563e3 100644
--- a/include/asm-x86_64/mce.h
+++ b/include/asm-x86_64/mce.h
@@ -105,6 +105,8 @@ extern atomic_t mce_entry;
 
 extern void do_machine_check(struct pt_regs *, long);
 
+extern int mce_notify_user(void);
+
 #endif
 
 #endif
diff --git a/include/asm-x86_64/thread_info.h b/include/asm-x86_64/thread_info.h
index 10bb5a8ed68..33c72ef15a0 100644
--- a/include/asm-x86_64/thread_info.h
+++ b/include/asm-x86_64/thread_info.h
@@ -115,6 +115,7 @@ static inline struct thread_info *stack_thread_info(void)
 #define TIF_SYSCALL_AUDIT       7       /* syscall auditing active */
 #define TIF_SECCOMP             8       /* secure computing */
 #define TIF_RESTORE_SIGMASK     9       /* restore signal mask in do_signal */
+#define TIF_MCE_NOTIFY          10      /* notify userspace of an MCE */
 /* 16 free */
 #define TIF_IA32                17      /* 32bit process */ 
 #define TIF_FORK                18      /* ret_from_fork */
@@ -133,6 +134,7 @@ static inline struct thread_info *stack_thread_info(void)
 #define _TIF_SYSCALL_AUDIT      (1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP            (1<<TIF_SECCOMP)
 #define _TIF_RESTORE_SIGMASK    (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_MCE_NOTIFY         (1<<TIF_MCE_NOTIFY)
 #define _TIF_IA32               (1<<TIF_IA32)
 #define _TIF_FORK               (1<<TIF_FORK)
 #define _TIF_ABI_PENDING        (1<<TIF_ABI_PENDING)