Commit 9a2bc860 authored by Linus Torvalds's avatar Linus Torvalds

Merge branch 'anton-kgdb' (kgdb dmesg fixups)

Merge emailed kgdb dmesg fixups patches from Anton Vorontsov:
 "The dmesg command appears to be broken after the printk rework.  The
  old logic in the kdb code makes no sense in terms of current
  printk/logging storage format, and KDB simply hangs forever upon
  entering 'dmesg' command.

  The first patch revives the command by switching to kmsg_dumper
  iterator.  As a side-effect, the code is now much more simpler.

  A few changes were needed in the printk.c: we needed unlocked variant
  of the kmsg_dumper iterator, but these can surely wait for 3.6.

  It's probably too late even for the first patch to go to 3.5, but I'll
  try to convince otherwise.  :-) Here we go:

   - The current code is broken for sure, and has no hope to work at
     all.  It is a regression
   - The new code works for me, and probably works for everyone else;
   - If it compiles (and I urge everyone to compile-test it on your
     setup), it hardly can make things worse."

* Merge emailed patches from Anton Vorontsov: (4 commits)
  kdb: Switch to nolock variants of kmsg_dump functions
  printk: Implement some unlocked kmsg_dump functions
  printk: Remove kdb_syslog_data
  kdb: Revive dmesg command
parents d75e2c9a c064da47
......@@ -55,12 +55,17 @@ struct kmsg_dumper {
#ifdef CONFIG_PRINTK
void kmsg_dump(enum kmsg_dump_reason reason);
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len);
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
void kmsg_dump_rewind(struct kmsg_dumper *dumper);
int kmsg_dump_register(struct kmsg_dumper *dumper);
......@@ -71,6 +76,13 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
{
}
static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
bool syslog, const char *line,
size_t size, size_t *len)
{
return false;
}
static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
const char *line, size_t size, size_t *len)
{
......@@ -83,6 +95,10 @@ static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
return false;
}
static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
{
}
static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
{
}
......
......@@ -14,6 +14,7 @@
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/kmsg_dump.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
......@@ -2040,8 +2041,15 @@ static int kdb_env(int argc, const char **argv)
*/
static int kdb_dmesg(int argc, const char **argv)
{
char *syslog_data[4], *start, *end, c = '\0', *p;
int diag, logging, logsize, lines = 0, adjust = 0, n;
int diag;
int logging;
int lines = 0;
int adjust = 0;
int n = 0;
int skip = 0;
struct kmsg_dumper dumper = { .active = 1 };
size_t len;
char buf[201];
if (argc > 2)
return KDB_ARGCOUNT;
......@@ -2064,22 +2072,10 @@ static int kdb_dmesg(int argc, const char **argv)
kdb_set(2, setargs);
}
/* syslog_data[0,1] physical start, end+1. syslog_data[2,3]
* logical start, end+1. */
kdb_syslog_data(syslog_data);
if (syslog_data[2] == syslog_data[3])
return 0;
logsize = syslog_data[1] - syslog_data[0];
start = syslog_data[2];
end = syslog_data[3];
#define KDB_WRAP(p) (((p - syslog_data[0]) % logsize) + syslog_data[0])
for (n = 0, p = start; p < end; ++p) {
c = *KDB_WRAP(p);
if (c == '\n')
++n;
}
if (c != '\n')
++n;
kmsg_dump_rewind_nolock(&dumper);
while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
n++;
if (lines < 0) {
if (adjust >= n)
kdb_printf("buffer only contains %d lines, nothing "
......@@ -2087,21 +2083,11 @@ static int kdb_dmesg(int argc, const char **argv)
else if (adjust - lines >= n)
kdb_printf("buffer only contains %d lines, last %d "
"lines printed\n", n, n - adjust);
if (adjust) {
for (; start < end && adjust; ++start) {
if (*KDB_WRAP(start) == '\n')
--adjust;
}
if (start < end)
++start;
}
for (p = start; p < end && lines; ++p) {
if (*KDB_WRAP(p) == '\n')
++lines;
}
end = p;
skip = adjust;
lines = abs(lines);
} else if (lines > 0) {
int skip = n - (adjust + lines);
skip = n - lines - adjust;
lines = abs(lines);
if (adjust >= n) {
kdb_printf("buffer only contains %d lines, "
"nothing printed\n", n);
......@@ -2112,35 +2098,24 @@ static int kdb_dmesg(int argc, const char **argv)
kdb_printf("buffer only contains %d lines, first "
"%d lines printed\n", n, lines);
}
for (; start < end && skip; ++start) {
if (*KDB_WRAP(start) == '\n')
--skip;
}
for (p = start; p < end && lines; ++p) {
if (*KDB_WRAP(p) == '\n')
--lines;
}
end = p;
} else {
lines = n;
}
/* Do a line at a time (max 200 chars) to reduce protocol overhead */
c = '\n';
while (start != end) {
char buf[201];
p = buf;
if (KDB_FLAG(CMD_INTERRUPT))
return 0;
while (start < end && (c = *KDB_WRAP(start)) &&
(p - buf) < sizeof(buf)-1) {
++start;
*p++ = c;
if (c == '\n')
break;
if (skip >= n || skip < 0)
return 0;
kmsg_dump_rewind_nolock(&dumper);
while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
if (skip) {
skip--;
continue;
}
*p = '\0';
kdb_printf("%s", buf);
if (!lines--)
break;
kdb_printf("%.*s\n", (int)len - 1, buf);
}
if (c != '\n')
kdb_printf("\n");
return 0;
}
......
......@@ -205,7 +205,6 @@ extern char kdb_grep_string[];
extern int kdb_grep_leading;
extern int kdb_grep_trailing;
extern char *kdb_cmds[];
extern void kdb_syslog_data(char *syslog_data[]);
extern unsigned long kdb_task_state_string(const char *);
extern char kdb_task_state_char (const struct task_struct *);
extern unsigned long kdb_task_state(const struct task_struct *p,
......
......@@ -1192,21 +1192,6 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
}
#ifdef CONFIG_KGDB_KDB
/* kdb dmesg command needs access to the syslog buffer. do_syslog()
* uses locks so it cannot be used during debugging. Just tell kdb
* where the start and end of the physical and logical logs are. This
* is equivalent to do_syslog(3).
*/
void kdb_syslog_data(char *syslog_data[4])
{
syslog_data[0] = log_buf;
syslog_data[1] = log_buf + log_buf_len;
syslog_data[2] = log_buf + log_first_idx;
syslog_data[3] = log_buf + log_next_idx;
}
#endif /* CONFIG_KGDB_KDB */
static bool __read_mostly ignore_loglevel;
static int __init ignore_loglevel_setup(char *str)
......@@ -2525,7 +2510,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
}
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
* @dumper: registered kmsg dumper
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
......@@ -2540,11 +2525,12 @@ 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(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len)
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
struct log *msg;
size_t l = 0;
bool ret = false;
......@@ -2552,7 +2538,6 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
if (!dumper->active)
goto out;
raw_spin_lock_irqsave(&logbuf_lock, flags);
if (dumper->cur_seq < log_first_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = log_first_seq;
......@@ -2560,10 +2545,8 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
}
/* last entry */
if (dumper->cur_seq >= log_next_seq) {
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
if (dumper->cur_seq >= log_next_seq)
goto out;
}
msg = log_from_idx(dumper->cur_idx);
l = msg_print_text(msg, 0, syslog, line, size);
......@@ -2571,12 +2554,41 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
dumper->cur_idx = log_next(dumper->cur_idx);
dumper->cur_seq++;
ret = true;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
out:
if (len)
*len = l;
return ret;
}
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* @dumper: registered kmsg dumper
* @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 *dumper, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
bool ret;
raw_spin_lock_irqsave(&logbuf_lock, flags);
ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
/**
......@@ -2678,6 +2690,24 @@ out:
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
/**
* kmsg_dump_rewind_nolock - reset the interator (unlocked version)
* @dumper: registered kmsg dumper
*
* 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 *dumper)
{
dumper->cur_seq = clear_seq;
dumper->cur_idx = clear_idx;
dumper->next_seq = log_next_seq;
dumper->next_idx = log_next_idx;
}
/**
* kmsg_dump_rewind - reset the interator
* @dumper: registered kmsg dumper
......@@ -2691,10 +2721,7 @@ void kmsg_dump_rewind(struct kmsg_dumper *dumper)
unsigned long flags;
raw_spin_lock_irqsave(&logbuf_lock, flags);
dumper->cur_seq = clear_seq;
dumper->cur_idx = clear_idx;
dumper->next_seq = log_next_seq;
dumper->next_idx = log_next_idx;
kmsg_dump_rewind_nolock(dumper);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
......
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