linuxkit/kernel/5.11.x-rt/patches/0032-0013-printk-kmsg_dump-remove-_nolock-variants.patch

From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 21 Dec 2020 10:27:58 +0106
Subject: [PATCH 13/28] printk: kmsg_dump: remove _nolock() variants

kmsg_dump_rewind() and kmsg_dump_get_line() are lockless, so there is
no need for _nolock() variants. Remove these functions and switch all
callers of the _nolock() variants.

The functions without _nolock() were chosen because they are already
exported to kernel modules.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 arch/powerpc/xmon/xmon.c    |    4 +-
 include/linux/kmsg_dump.h   |   18 -------------
 kernel/debug/kdb/kdb_main.c |    8 ++---
 kernel/printk/printk.c      |   60 +++++---------------------------------------
 4 files changed, 15 insertions(+), 75 deletions(-)

--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3017,9 +3017,9 @@ dump_log_buf(void)
 	catch_memory_errors = 1;
 	sync();
 
-	kmsg_dump_rewind_nolock(&iter);
+	kmsg_dump_rewind(&iter);
 	xmon_start_pagination();
-	while (kmsg_dump_get_line_nolock(&iter, false, buf, sizeof(buf), &len)) {
+	while (kmsg_dump_get_line(&iter, false, buf, sizeof(buf), &len)) {
 		buf[len] = '\0';
 		printf("%s", buf);
 	}
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -60,18 +60,13 @@ struct kmsg_dumper {
 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);
 
-bool kmsg_dump_get_line_nolock(struct kmsg_dumper_iter *iter, bool syslog,
-			       char *line, size_t size, size_t *len);
-
 bool kmsg_dump_get_line(struct kmsg_dumper_iter *iter, bool syslog,
 			char *line, size_t size, size_t *len);
 
 bool kmsg_dump_get_buffer(struct kmsg_dumper_iter *iter, bool syslog,
 			  char *buf, size_t size, size_t *len_out);
 
-void kmsg_dump_rewind_nolock(struct kmsg_dumper_iter *iter);
-
-void kmsg_dump_rewind(struct kmsg_dumper_iter *dumper_iter);
+void kmsg_dump_rewind(struct kmsg_dumper_iter *iter);
 
 int kmsg_dump_register(struct kmsg_dumper *dumper);
 
@@ -83,13 +78,6 @@ static inline void kmsg_dump(enum kmsg_d
 {
 }
 
-static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper_iter *iter,
-					     bool syslog, const char *line,
-					     size_t size, size_t *len)
-{
-	return false;
-}
-
 static inline bool kmsg_dump_get_line(struct kmsg_dumper_iter *iter, bool syslog,
 				const char *line, size_t size, size_t *len)
 {
@@ -102,10 +90,6 @@ static inline bool kmsg_dump_get_buffer(
 	return false;
 }
 
-static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper_iter *iter)
-{
-}
-
 static inline void kmsg_dump_rewind(struct kmsg_dumper_iter *iter)
 {
 }
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2126,8 +2126,8 @@ static int kdb_dmesg(int argc, const cha
 		kdb_set(2, setargs);
 	}
 
-	kmsg_dump_rewind_nolock(&iter);
-	while (kmsg_dump_get_line_nolock(&iter, 1, NULL, 0, NULL))
+	kmsg_dump_rewind(&iter);
+	while (kmsg_dump_get_line(&iter, 1, NULL, 0, NULL))
 		n++;
 
 	if (lines < 0) {
@@ -2159,8 +2159,8 @@ static int kdb_dmesg(int argc, const cha
 	if (skip >= n || skip < 0)
 		return 0;
 
-	kmsg_dump_rewind_nolock(&iter);
-	while (kmsg_dump_get_line_nolock(&iter, 1, buf, sizeof(buf), &len)) {
+	kmsg_dump_rewind(&iter);
+	while (kmsg_dump_get_line(&iter, 1, buf, sizeof(buf), &len)) {
 		if (skip) {
 			skip--;
 			continue;
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3382,7 +3382,7 @@ void kmsg_dump(enum kmsg_dump_reason rea
 }
 
 /**
- * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
+ * kmsg_dump_get_line - retrieve one kmsg log line
  * @iter: kmsg dumper iterator
  * @syslog: include the "<4>" prefixes
  * @line: buffer to copy the line to
@@ -3397,18 +3397,18 @@ void kmsg_dump(enum kmsg_dump_reason rea
  *
  * A return value of FALSE indicates that there are no more records to
  * read.
- *
- * The function is similar to kmsg_dump_get_line(), but grabs no locks.
  */
-bool kmsg_dump_get_line_nolock(struct kmsg_dumper_iter *iter, bool syslog,
-			       char *line, size_t size, size_t *len)
+bool kmsg_dump_get_line(struct kmsg_dumper_iter *iter, bool syslog,
+			char *line, size_t size, size_t *len)
 {
 	struct printk_info info;
 	unsigned int line_count;
 	struct printk_record r;
+	unsigned long flags;
 	size_t l = 0;
 	bool ret = false;
 
+	printk_safe_enter_irqsave(flags);
 	prb_rec_init_rd(&r, &info, line, size);
 
 	if (!iter->active)
@@ -3432,40 +3432,11 @@ bool kmsg_dump_get_line_nolock(struct km
 	iter->cur_seq = r.info->seq + 1;
 	ret = true;
 out:
+	printk_safe_exit_irqrestore(flags);
 	if (len)
 		*len = l;
 	return ret;
 }
-
-/**
- * kmsg_dump_get_line - retrieve one kmsg log line
- * @iter: kmsg dumper iterator
- * @syslog: include the "<4>" prefixes
- * @line: buffer to copy the line to
- * @size: maximum size of the buffer
- * @len: length of line placed into buffer
- *
- * Start at the beginning of the kmsg buffer, with the oldest kmsg
- * record, and copy one record into the provided buffer.
- *
- * Consecutive calls will return the next available record moving
- * towards the end of the buffer with the youngest messages.
- *
- * A return value of FALSE indicates that there are no more records to
- * read.
- */
-bool kmsg_dump_get_line(struct kmsg_dumper_iter *iter, bool syslog,
-			char *line, size_t size, size_t *len)
-{
-	unsigned long flags;
-	bool ret;
-
-	printk_safe_enter_irqsave(flags);
-	ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
-	printk_safe_exit_irqrestore(flags);
-
-	return ret;
-}
 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
 
 /**
@@ -3555,22 +3526,6 @@ bool kmsg_dump_get_buffer(struct kmsg_du
 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
 
 /**
- * kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
- * @iter: kmsg dumper iterator
- *
- * Reset the dumper's iterator so that kmsg_dump_get_line() and
- * kmsg_dump_get_buffer() can be called again and used multiple
- * times within the same dumper.dump() callback.
- *
- * The function is similar to kmsg_dump_rewind(), but grabs no locks.
- */
-void kmsg_dump_rewind_nolock(struct kmsg_dumper_iter *iter)
-{
-	iter->cur_seq = latched_seq_read_nolock(&clear_seq);
-	iter->next_seq = prb_next_seq(prb);
-}
-
-/**
  * kmsg_dump_rewind - reset the iterator
  * @iter: kmsg dumper iterator
  *
@@ -3583,7 +3538,8 @@ void kmsg_dump_rewind(struct kmsg_dumper
 	unsigned long flags;
 
 	printk_safe_enter_irqsave(flags);
-	kmsg_dump_rewind_nolock(iter);
+	iter->cur_seq = latched_seq_read_nolock(&clear_seq);
+	iter->next_seq = prb_next_seq(prb);
 	printk_safe_exit_irqrestore(flags);
 }
 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);