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-rw-r--r--include/linux/printk.h4
-rw-r--r--kernel/printk/internal.h9
-rw-r--r--kernel/printk/printk.c57
-rw-r--r--kernel/printk/printk_safe.c58
-rw-r--r--kernel/trace/trace.c4
-rw-r--r--lib/nmi_backtrace.c3
6 files changed, 87 insertions, 48 deletions
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 18602bb3eca8..cf3eccfe1543 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -148,9 +148,13 @@ void early_printk(const char *s, ...) { }
#ifdef CONFIG_PRINTK_NMI
extern void printk_nmi_enter(void);
extern void printk_nmi_exit(void);
+extern void printk_nmi_direct_enter(void);
+extern void printk_nmi_direct_exit(void);
#else
static inline void printk_nmi_enter(void) { }
static inline void printk_nmi_exit(void) { }
+static inline void printk_nmi_direct_enter(void) { }
+static inline void printk_nmi_direct_exit(void) { }
#endif /* PRINTK_NMI */
#ifdef CONFIG_PRINTK
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 2a7d04049af4..0f1898820cba 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -19,11 +19,16 @@
#ifdef CONFIG_PRINTK
#define PRINTK_SAFE_CONTEXT_MASK 0x3fffffff
-#define PRINTK_NMI_DEFERRED_CONTEXT_MASK 0x40000000
+#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x40000000
#define PRINTK_NMI_CONTEXT_MASK 0x80000000
extern raw_spinlock_t logbuf_lock;
+__printf(5, 0)
+int vprintk_store(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args);
+
__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);
@@ -54,6 +59,8 @@ void __printk_safe_exit(void);
local_irq_enable(); \
} while (0)
+void defer_console_output(void);
+
#else
__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e2cb0fc18e2d..9a63aeeaaf5d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1829,28 +1829,16 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
}
-asmlinkage int vprintk_emit(int facility, int level,
- const char *dict, size_t dictlen,
- const char *fmt, va_list args)
+/* Must be called under logbuf_lock. */
+int vprintk_store(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args)
{
static char textbuf[LOG_LINE_MAX];
char *text = textbuf;
size_t text_len;
enum log_flags lflags = 0;
- unsigned long flags;
- int printed_len;
- bool in_sched = false;
-
- if (level == LOGLEVEL_SCHED) {
- level = LOGLEVEL_DEFAULT;
- in_sched = true;
- }
-
- boot_delay_msec(level);
- printk_delay();
- /* This stops the holder of console_sem just where we want him */
- logbuf_lock_irqsave(flags);
/*
* The printf needs to come first; we need the syslog
* prefix which might be passed-in as a parameter.
@@ -1894,8 +1882,29 @@ asmlinkage int vprintk_emit(int facility, int level,
if (suppress_message_printing(level))
lflags |= LOG_NOCONS;
- printed_len = log_output(facility, level, lflags, dict, dictlen, text, text_len);
+ return log_output(facility, level, lflags,
+ dict, dictlen, text, text_len);
+}
+asmlinkage int vprintk_emit(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args)
+{
+ int printed_len;
+ bool in_sched = false;
+ unsigned long flags;
+
+ if (level == LOGLEVEL_SCHED) {
+ level = LOGLEVEL_DEFAULT;
+ in_sched = true;
+ }
+
+ boot_delay_msec(level);
+ printk_delay();
+
+ /* This stops the holder of console_sem just where we want him */
+ logbuf_lock_irqsave(flags);
+ printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
logbuf_unlock_irqrestore(flags);
/* If called from the scheduler, we can not call up(). */
@@ -2884,16 +2893,20 @@ void wake_up_klogd(void)
preempt_enable();
}
-int vprintk_deferred(const char *fmt, va_list args)
+void defer_console_output(void)
{
- 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();
+}
+
+int vprintk_deferred(const char *fmt, va_list args)
+{
+ int r;
+
+ r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
+ defer_console_output();
return r;
}
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index d7d091309054..a0a74c533e4b 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -308,24 +308,33 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
void printk_nmi_enter(void)
{
- /*
- * 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);
- }
+ this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
}
void printk_nmi_exit(void)
{
- this_cpu_and(printk_context,
- ~(PRINTK_NMI_CONTEXT_MASK |
- PRINTK_NMI_DEFERRED_CONTEXT_MASK));
+ this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
+}
+
+/*
+ * Marks a code that might produce many messages in NMI context
+ * and the risk of losing them is more critical than eventual
+ * reordering.
+ *
+ * It has effect only when called in NMI context. Then printk()
+ * will try to store the messages into the main logbuf directly
+ * and use the per-CPU buffers only as a fallback when the lock
+ * is not available.
+ */
+void printk_nmi_direct_enter(void)
+{
+ if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
+ this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);
+}
+
+void printk_nmi_direct_exit(void)
+{
+ this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
}
#else
@@ -363,6 +372,20 @@ void __printk_safe_exit(void)
__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
{
+ /*
+ * Try to use the main logbuf even in NMI. But avoid calling console
+ * drivers that might have their own locks.
+ */
+ if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&
+ raw_spin_trylock(&logbuf_lock)) {
+ int len;
+
+ len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
+ raw_spin_unlock(&logbuf_lock);
+ defer_console_output();
+ return len;
+ }
+
/* 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);
@@ -371,13 +394,6 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
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/kernel/trace/trace.c b/kernel/trace/trace.c
index bcd93031d042..f106ad12f72f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8265,6 +8265,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
tracing_off();
local_irq_save(flags);
+ printk_nmi_direct_enter();
/* Simulate the iterator */
trace_init_global_iter(&iter);
@@ -8344,7 +8345,8 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
for_each_tracing_cpu(cpu) {
atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
}
- atomic_dec(&dump_running);
+ atomic_dec(&dump_running);
+ printk_nmi_direct_exit();
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(ftrace_dump);
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 61a6b5aab07e..15ca78e1c7d4 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -87,11 +87,9 @@ 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 %pS\n",
cpu, (void *)instruction_pointer(regs));
@@ -102,7 +100,6 @@ 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;
}