[PATCHv7 2/8] printk: rename nmi.c and exported api

From: Sergey Senozhatsky
Date: Tue Dec 27 2016 - 09:17:29 EST

A preparation patch for printk_safe work. No functional change.
- rename nmi.c to print_safe.c
- add `printk_safe' prefix to some (which used both by printk-safe
and printk-nmi) of the exported functions.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
include/linux/printk.h | 12 +++----
init/Kconfig | 16 +++++----
init/main.c | 2 +-
kernel/kexec_core.c | 2 +-
kernel/panic.c | 4 +--
kernel/printk/Makefile | 2 +-
kernel/printk/{nmi.c => printk_safe.c} | 64 +++++++++++++++++-----------------
lib/nmi_backtrace.c | 2 +-
8 files changed, 53 insertions(+), 51 deletions(-)
rename kernel/printk/{nmi.c => printk_safe.c} (79%)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 3472cc6b7a60..37e933eeffb2 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -147,17 +147,17 @@ void early_printk(const char *s, ...) { }
#endif

#ifdef CONFIG_PRINTK_NMI
-extern void printk_nmi_init(void);
+extern void printk_safe_init(void);
extern void printk_nmi_enter(void);
extern void printk_nmi_exit(void);
-extern void printk_nmi_flush(void);
-extern void printk_nmi_flush_on_panic(void);
+extern void printk_safe_flush(void);
+extern void printk_safe_flush_on_panic(void);
#else
-static inline void printk_nmi_init(void) { }
+static inline void printk_safe_init(void) { }
static inline void printk_nmi_enter(void) { }
static inline void printk_nmi_exit(void) { }
-static inline void printk_nmi_flush(void) { }
-static inline void printk_nmi_flush_on_panic(void) { }
+static inline void printk_safe_flush(void) { }
+static inline void printk_safe_flush_on_panic(void) { }
#endif /* PRINTK_NMI */

#ifdef CONFIG_PRINTK
diff --git a/init/Kconfig b/init/Kconfig
index 223b734abccd..760b7d0bc9d7 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -875,17 +875,19 @@ config LOG_CPU_MAX_BUF_SHIFT
13 => 8 KB for each CPU
12 => 4 KB for each CPU

-config NMI_LOG_BUF_SHIFT
- int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
+config PRINTK_SAFE_LOG_BUF_SHIFT
+ int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
range 10 21
default 13
- depends on PRINTK_NMI
+ depends on PRINTK
help
- Select the size of a per-CPU buffer where NMI messages are temporary
- stored. They are copied to the main log buffer in a safe context
- to avoid a deadlock. The value defines the size as a power of 2.
+ Select the size of an alternate printk per-CPU buffer where messages
+ printed from usafe contexts are temporary stored. One example would
+ be NMI messages, another one - printk recursion. The messages are
+ copied to the main log buffer in a safe context to avoid a deadlock.
+ The value defines the size as a power of 2.

- NMI messages are rare and limited. The largest one is when
+ Those messages are rare and limited. The largest one is when
a backtrace is printed. It usually fits into 4KB. Select
8KB if you want to be on the safe side.

diff --git a/init/main.c b/init/main.c
index b8f88013462d..b08305a7138c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -579,7 +579,7 @@ asmlinkage __visible void __init start_kernel(void)
timekeeping_init();
time_init();
sched_clock_postinit();
- printk_nmi_init();
+ printk_safe_init();
perf_event_init();
profile_init();
call_function_init();
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5617cc412444..14bb9eb76665 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -916,7 +916,7 @@ void crash_kexec(struct pt_regs *regs)
old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
if (old_cpu == PANIC_CPU_INVALID) {
/* This is the 1st CPU which comes here, so go ahead. */
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
__crash_kexec(regs);

/*
diff --git a/kernel/panic.c b/kernel/panic.c
index c51edaa04fce..8c8efcd310e7 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -188,7 +188,7 @@ void panic(const char *fmt, ...)
* Bypass the panic_cpu check and call __crash_kexec directly.
*/
if (!_crash_kexec_post_notifiers) {
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
__crash_kexec(NULL);

/*
@@ -213,7 +213,7 @@ void panic(const char *fmt, ...)
atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

/* Call flush even twice. It tries harder with a single online CPU */
- printk_nmi_flush_on_panic();
+ printk_safe_flush_on_panic();
kmsg_dump(KMSG_DUMP_PANIC);

/*
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index abb0042a427b..607928119f26 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -1,3 +1,3 @@
obj-y = printk.o
-obj-$(CONFIG_PRINTK_NMI) += nmi.o
+obj-$(CONFIG_PRINTK_NMI) += printk_safe.o
obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o
diff --git a/kernel/printk/nmi.c b/kernel/printk/printk_safe.c
similarity index 79%
rename from kernel/printk/nmi.c
rename to kernel/printk/printk_safe.c
index f011aaef583c..fc80359dcd78 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/printk_safe.c
@@ -1,5 +1,5 @@
/*
- * nmi.c - Safe printk in NMI context
+ * printk_safe.c - Safe printk in NMI context
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -39,18 +39,18 @@
* were handled or when IRQs are blocked.
*/
DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
-static int printk_nmi_irq_ready;
+static int printk_safe_irq_ready;
atomic_t nmi_message_lost;

-#define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) - \
+#define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) - \
sizeof(atomic_t) - sizeof(struct irq_work))

-struct nmi_seq_buf {
+struct printk_safe_seq_buf {
atomic_t len; /* length of written data */
struct irq_work work; /* IRQ work that flushes the buffer */
- unsigned char buffer[NMI_LOG_BUF_LEN];
+ unsigned char buffer[SAFE_LOG_BUF_LEN];
};
-static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
+static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);

/*
* Safe printk() for NMI context. It uses a per-CPU buffer to
@@ -60,7 +60,7 @@ static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
*/
static int vprintk_nmi(const char *fmt, va_list args)
{
- struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
+ struct printk_safe_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
int add = 0;
size_t len;

@@ -91,7 +91,7 @@ static int vprintk_nmi(const char *fmt, va_list args)
goto again;

/* Get flushed in a more safe context. */
- if (add && printk_nmi_irq_ready) {
+ if (add && printk_safe_irq_ready) {
/* Make sure that IRQ work is really initialized. */
smp_rmb();
irq_work_queue(&s->work);
@@ -100,7 +100,7 @@ static int vprintk_nmi(const char *fmt, va_list args)
return add;
}

-static void printk_nmi_flush_line(const char *text, int len)
+static void printk_safe_flush_line(const char *text, int len)
{
/*
* The buffers are flushed in NMI only on panic. The messages must
@@ -111,11 +111,10 @@ static void printk_nmi_flush_line(const char *text, int len)
printk_deferred("%.*s", len, text);
else
printk("%.*s", len, text);
-
}

/* printk part of the temporary buffer line by line */
-static int printk_nmi_flush_buffer(const char *start, size_t len)
+static int printk_safe_flush_buffer(const char *start, size_t len)
{
const char *c, *end;
bool header;
@@ -127,7 +126,7 @@ static int printk_nmi_flush_buffer(const char *start, size_t len)
/* Print line by line. */
while (c < end) {
if (*c == '\n') {
- printk_nmi_flush_line(start, c - start + 1);
+ printk_safe_flush_line(start, c - start + 1);
start = ++c;
header = true;
continue;
@@ -140,7 +139,7 @@ static int printk_nmi_flush_buffer(const char *start, size_t len)
continue;
}

- printk_nmi_flush_line(start, c - start);
+ printk_safe_flush_line(start, c - start);
start = c++;
header = true;
continue;
@@ -154,8 +153,8 @@ static int printk_nmi_flush_buffer(const char *start, size_t len)
if (start < end && !header) {
static const char newline[] = KERN_CONT "\n";

- printk_nmi_flush_line(start, end - start);
- printk_nmi_flush_line(newline, strlen(newline));
+ printk_safe_flush_line(start, end - start);
+ printk_safe_flush_line(newline, strlen(newline));
}

return len;
@@ -165,11 +164,12 @@ static int printk_nmi_flush_buffer(const char *start, size_t len)
* Flush data from the associated per_CPU buffer. The function
* can be called either via IRQ work or independently.
*/
-static void __printk_nmi_flush(struct irq_work *work)
+static void __printk_safe_flush(struct irq_work *work)
{
static raw_spinlock_t read_lock =
__RAW_SPIN_LOCK_INITIALIZER(read_lock);
- struct nmi_seq_buf *s = container_of(work, struct nmi_seq_buf, work);
+ struct printk_safe_seq_buf *s =
+ container_of(work, struct printk_safe_seq_buf, work);
unsigned long flags;
size_t len;
int i;
@@ -194,9 +194,9 @@ static void __printk_nmi_flush(struct irq_work *work)
* buffer size.
*/
if ((i && i >= len) || len > sizeof(s->buffer)) {
- const char *msg = "printk_nmi_flush: internal error\n";
+ const char *msg = "printk_safe_flush: internal error\n";

- printk_nmi_flush_line(msg, strlen(msg));
+ printk_safe_flush_line(msg, strlen(msg));
len = 0;
}

@@ -205,7 +205,7 @@ static void __printk_nmi_flush(struct irq_work *work)

/* Make sure that data has been written up to the @len */
smp_rmb();
- i += printk_nmi_flush_buffer(s->buffer + i, len - i);
+ i += printk_safe_flush_buffer(s->buffer + i, len - i);

/*
* Check that nothing has got added in the meantime and truncate
@@ -221,31 +221,31 @@ static void __printk_nmi_flush(struct irq_work *work)
}

/**
- * printk_nmi_flush - flush all per-cpu nmi buffers.
+ * printk_safe_flush - flush all per-cpu nmi buffers.
*
* The buffers are flushed automatically via IRQ work. This function
* is useful only when someone wants to be sure that all buffers have
* been flushed at some point.
*/
-void printk_nmi_flush(void)
+void printk_safe_flush(void)
{
int cpu;

for_each_possible_cpu(cpu)
- __printk_nmi_flush(&per_cpu(nmi_print_seq, cpu).work);
+ __printk_safe_flush(&per_cpu(nmi_print_seq, cpu).work);
}

/**
- * printk_nmi_flush_on_panic - flush all per-cpu nmi buffers when the system
+ * printk_safe_flush_on_panic - flush all per-cpu nmi buffers when the system
* goes down.
*
- * Similar to printk_nmi_flush() but it can be called even in NMI context when
+ * Similar to printk_safe_flush() but it can be called even in NMI context when
* the system goes down. It does the best effort to get NMI messages into
* the main ring buffer.
*
* Note that it could try harder when there is only one CPU online.
*/
-void printk_nmi_flush_on_panic(void)
+void printk_safe_flush_on_panic(void)
{
/*
* Make sure that we could access the main ring buffer.
@@ -259,25 +259,25 @@ void printk_nmi_flush_on_panic(void)
raw_spin_lock_init(&logbuf_lock);
}

- printk_nmi_flush();
+ printk_safe_flush();
}

-void __init printk_nmi_init(void)
+void __init printk_safe_init(void)
{
int cpu;

for_each_possible_cpu(cpu) {
- struct nmi_seq_buf *s = &per_cpu(nmi_print_seq, cpu);
+ struct printk_safe_seq_buf *s = &per_cpu(nmi_print_seq, cpu);

- init_irq_work(&s->work, __printk_nmi_flush);
+ init_irq_work(&s->work, __printk_safe_flush);
}

/* Make sure that IRQ works are initialized before enabling. */
smp_wmb();
- printk_nmi_irq_ready = 1;
+ printk_safe_irq_ready = 1;

/* Flush pending messages that did not have scheduled IRQ works. */
- printk_nmi_flush();
+ printk_safe_flush();
}

void printk_nmi_enter(void)
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 75554754eadf..5f7999eacad5 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -77,7 +77,7 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
* Force flush any remote buffers that might be stuck in IRQ context
* and therefore could not run their irq_work.
*/
- printk_nmi_flush();
+ printk_safe_flush();

clear_bit_unlock(0, &backtrace_flag);
put_cpu();
--
2.11.0