[PATCH] x86-64: Safe interrupts in oops_begin/end

Rather than blindly re-enabling interrupts in oops_end(), save their state
in oope_begin() and then restore that state.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 29 insertions, 25 deletions

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index f238d6078a5a..64a59cb49411 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -343,30 +343,33 @@ void out_of_line_bug(void)
 static DEFINE_SPINLOCK(die_lock);
 static int die_owner = -1;
 
-void oops_begin(void)
+unsigned long oops_begin(void)
 {
-        int cpu = safe_smp_processor_id(); 
-        /* racy, but better than risking deadlock. */ 
-        local_irq_disable();
+        int cpu = safe_smp_processor_id();
+        unsigned long flags;
+
+        /* racy, but better than risking deadlock. */
+        local_irq_save(flags);
         if (!spin_trylock(&die_lock)) { 
                 if (cpu == die_owner) 
                         /* nested oops. should stop eventually */;
                 else
-                        spin_lock(&die_lock); 
+                        spin_lock(&die_lock);
         }
-        die_owner = cpu; 
+        die_owner = cpu;
         console_verbose();
-        bust_spinlocks(1); 
+        bust_spinlocks(1);
+        return flags;
 }
 
-void oops_end(void)
+void oops_end(unsigned long flags)
 { 
         die_owner = -1;
-        bust_spinlocks(0); 
-        spin_unlock(&die_lock); 
+        bust_spinlocks(0);
+        spin_unlock_irqrestore(&die_lock, flags);
         if (panic_on_oops)
-                panic("Oops"); 
-} 
+                panic("Oops");
+}
 
 void __die(const char * str, struct pt_regs * regs, long err)
 {
@@ -392,10 +395,11 @@ void __die(const char * str, struct pt_regs * regs, long err)
 
 void die(const char * str, struct pt_regs * regs, long err)
 {
-        oops_begin();
+        unsigned long flags = oops_begin();
+
         handle_BUG(regs);
         __die(str, regs, err);
-        oops_end();
+        oops_end(flags);
         do_exit(SIGSEGV); 
 }
 static inline void die_if_kernel(const char * str, struct pt_regs * regs, long err)
@@ -406,7 +410,8 @@ static inline void die_if_kernel(const char * str, struct pt_regs * regs, long e
 
 void die_nmi(char *str, struct pt_regs *regs)
 {
-        oops_begin();
+        unsigned long flags = oops_begin();
+
         /*
          * We are in trouble anyway, lets at least try
          * to get a message out.
@@ -416,7 +421,7 @@ void die_nmi(char *str, struct pt_regs *regs)
         if (panic_on_timeout || panic_on_oops)
                 panic("nmi watchdog");
         printk("console shuts up ...\n");
-        oops_end();
+        oops_end(flags);
         do_exit(SIGSEGV);
 }
 
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 816732d8858c..b75b872ec154 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -221,12 +221,13 @@ int unhandled_signal(struct task_struct *tsk, int sig)
 static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
                                  unsigned long error_code)
 {
-        oops_begin();
+        unsigned long flags = oops_begin();
+
         printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
                current->comm, address);
         dump_pagetable(address);
         __die("Bad pagetable", regs, error_code);
-        oops_end();
+        oops_end(flags);
         do_exit(SIGKILL);
 }
 
@@ -304,6 +305,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
         unsigned long address;
         const struct exception_table_entry *fixup;
         int write;
+        unsigned long flags;
         siginfo_t info;
 
 #ifdef CONFIG_CHECKING
@@ -521,7 +523,7 @@ no_context:
  * terminate things with extreme prejudice.
  */
 
-        oops_begin(); 
+        flags = oops_begin();
 
         if (address < PAGE_SIZE)
                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
@@ -534,7 +536,7 @@ no_context:
         __die("Oops", regs, error_code);
         /* Executive summary in case the body of the oops scrolled away */
         printk(KERN_EMERG "CR2: %016lx\n", address);
-        oops_end(); 
+        oops_end(flags);
         do_exit(SIGKILL);
 
 /*
diff --git a/include/asm-x86_64/kdebug.h b/include/asm-x86_64/kdebug.h
index b90341994d80..f604e84c5303 100644
--- a/include/asm-x86_64/kdebug.h
+++ b/include/asm-x86_64/kdebug.h
@@ -46,7 +46,7 @@ extern void die(const char *,struct pt_regs *,long);
 extern void __die(const char *,struct pt_regs *,long);
 extern void show_registers(struct pt_regs *regs);
 extern void dump_pagetable(unsigned long);
-extern void oops_begin(void);
-extern void oops_end(void);
+extern unsigned long oops_begin(void);
+extern void oops_end(unsigned long);
 
 #endif
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index 764b5f822ce2..dbb37b0adb43 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -74,9 +74,6 @@ extern void acpi_reserve_bootmem(void);
 
 extern void swap_low_mappings(void);
 
-extern void oops_begin(void);
-extern void die(const char *,struct pt_regs *,long);
-extern void __die(const char * str, struct pt_regs * regs, long err);
 extern void __show_regs(struct pt_regs * regs);
 extern void show_regs(struct pt_regs * regs);