Merge branch 'for-4.13' into for-linus
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 1db044f..2a7d040 100644
--- 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
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2720,20 +2720,29 @@ void wake_up_klogd(void)
preempt_enable();
}
+int vprintk_deferred(const char *fmt, va_list args)
+{
+ int r;
+
+ r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
+
+ preempt_disable();
+ __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+ irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
+ preempt_enable();
+
+ return r;
+}
+
int printk_deferred(const char *fmt, ...)
{
va_list args;
int r;
- preempt_disable();
va_start(args, fmt);
- r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
+ r = vprintk_deferred(fmt, args);
va_end(args);
- __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
- irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
- preempt_enable();
-
return r;
}
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 033e50a..3cdaeae 100644
--- 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
--- 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;
}