[PATCH printk-rework 12/14] printk: kmsg_dump: remove _nolock() variants

John Ogness
2021-02-18T09:40:06Z

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(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 43162b885259..4cac114ba32d 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3015,9 +3015,9 @@ 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);
}
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 2fdb10ab1799..86673930c8ea 100644
--- 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_dump_reason reason)
{
}

-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(struct kmsg_dumper_iter *iter, bool sysl
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)
{
}
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 7ae9da245e4b..dbf1d126ac5e 100644
--- 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 char **argv)
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 char **argv)
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;
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c5ea46ed88c7..744b806d5457 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3378,7 +3378,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
}

/**
- * 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
@@ -3393,18 +3393,18 @@ void kmsg_dump(enum kmsg_dump_reason reason)
*
* 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)
@@ -3428,40 +3428,11 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper_iter *iter, bool syslog,
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);

/**
@@ -3550,22 +3521,6 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper_iter *iter, bool syslog,
}
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
@@ -3579,7 +3534,8 @@ void kmsg_dump_rewind(struct kmsg_dumper_iter *iter)
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);
--
2.20.1