Merge branch 'for-4.13' into for-linus

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 1db044f..2a7d040 100644 (file)
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -18,12 +18,14 @@
 
 #ifdef CONFIG_PRINTK
 
-#define PRINTK_SAFE_CONTEXT_MASK       0x7fffffff
-#define PRINTK_NMI_CONTEXT_MASK        0x80000000
+#define PRINTK_SAFE_CONTEXT_MASK        0x3fffffff
+#define PRINTK_NMI_DEFERRED_CONTEXT_MASK 0x40000000
+#define PRINTK_NMI_CONTEXT_MASK                 0x80000000
 
 extern raw_spinlock_t logbuf_lock;
 
 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
+__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
 __printf(1, 0) int vprintk_func(const char *fmt, va_list args);
 void __printk_safe_enter(void);
 void __printk_safe_exit(void);

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a1db38a..8603a48 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2720,16 +2720,13 @@ void wake_up_klogd(void)
        preempt_enable();
 }
 
-int printk_deferred(const char *fmt, ...)
+int vprintk_deferred(const char *fmt, va_list args)
 {
-       va_list args;
        int r;
 
-       preempt_disable();
-       va_start(args, fmt);
        r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
-       va_end(args);
 
+       preempt_disable();
        __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
        irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
        preempt_enable();
@@ -2737,6 +2734,18 @@ int printk_deferred(const char *fmt, ...)
        return r;
 }
 
+int printk_deferred(const char *fmt, ...)
+{
+       va_list args;
+       int r;
+
+       va_start(args, fmt);
+       r = vprintk_deferred(fmt, args);
+       va_end(args);
+
+       return r;
+}
+
 /*
  * printk rate limiting, lifted from the networking subsystem.
  *

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 033e50a..3cdaeae 100644 (file)
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -80,8 +80,8 @@ static void queue_flush_work(struct printk_safe_seq_buf *s)
  * happen, printk_safe_log_store() will notice the buffer->len mismatch
  * and repeat the write.
  */
-static int printk_safe_log_store(struct printk_safe_seq_buf *s,
-                                const char *fmt, va_list args)
+static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
+                                               const char *fmt, va_list args)
 {
        int add;
        size_t len;
@@ -299,7 +299,7 @@ void printk_safe_flush_on_panic(void)
  * one writer running. But the buffer might get flushed from another
  * CPU, so we need to be careful.
  */
-static int vprintk_nmi(const char *fmt, va_list args)
+static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
 {
        struct printk_safe_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
 
@@ -308,17 +308,29 @@ static int vprintk_nmi(const char *fmt, va_list args)
 
 void printk_nmi_enter(void)
 {
-       this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
+       /*
+        * The size of the extra per-CPU buffer is limited. Use it only when
+        * the main one is locked. If this CPU is not in the safe context,
+        * the lock must be taken on another CPU and we could wait for it.
+        */
+       if ((this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) &&
+           raw_spin_is_locked(&logbuf_lock)) {
+               this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
+       } else {
+               this_cpu_or(printk_context, PRINTK_NMI_DEFERRED_CONTEXT_MASK);
+       }
 }
 
 void printk_nmi_exit(void)
 {
-       this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
+       this_cpu_and(printk_context,
+                    ~(PRINTK_NMI_CONTEXT_MASK |
+                      PRINTK_NMI_DEFERRED_CONTEXT_MASK));
 }
 
 #else
 
-static int vprintk_nmi(const char *fmt, va_list args)
+static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
 {
        return 0;
 }
@@ -330,7 +342,7 @@ static int vprintk_nmi(const char *fmt, va_list args)
  * into itself. It uses a per-CPU buffer to store the message, just like
  * NMI.
  */
-static int vprintk_safe(const char *fmt, va_list args)
+static __printf(1, 0) int vprintk_safe(const char *fmt, va_list args)
 {
        struct printk_safe_seq_buf *s = this_cpu_ptr(&safe_print_seq);
 
@@ -351,12 +363,22 @@ void __printk_safe_exit(void)
 
 __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
 {
+       /* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */
        if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
                return vprintk_nmi(fmt, args);
 
+       /* Use extra buffer to prevent a recursion deadlock in safe mode. */
        if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK)
                return vprintk_safe(fmt, args);
 
+       /*
+        * Use the main logbuf when logbuf_lock is available in NMI.
+        * But avoid calling console drivers that might have their own locks.
+        */
+       if (this_cpu_read(printk_context) & PRINTK_NMI_DEFERRED_CONTEXT_MASK)
+               return vprintk_deferred(fmt, args);
+
+       /* No obstacles. */
        return vprintk_default(fmt, args);
 }
 

diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 4e8a30d..0bc0a35 100644 (file)
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -86,9 +86,11 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
 
 bool nmi_cpu_backtrace(struct pt_regs *regs)
 {
+       static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
        int cpu = smp_processor_id();
 
        if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
+               arch_spin_lock(&lock);
                if (regs && cpu_in_idle(instruction_pointer(regs))) {
                        pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
                                cpu, instruction_pointer(regs));
@@ -99,6 +101,7 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
                        else
                                dump_stack();
                }
+               arch_spin_unlock(&lock);
                cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
                return true;
        }