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printk: convert the rest to printk-safe
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This patch converts the rest of logbuf users (which are
out of printk recursion case, but can deadlock in printk).
To make printk-safe usage easier the patch introduces 4
helper macros:
- logbuf_lock_irq()/logbuf_unlock_irq()
  lock/unlock the logbuf lock and disable/enable local IRQ

- logbuf_lock_irqsave(flags)/logbuf_unlock_irqrestore(flags)
  lock/unlock the logbuf lock and saves/restores local IRQ state

Link: http://lkml.kernel.org/r/20161227141611.940-9-sergey.senozhatsky@gmail.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Calvin Owens <calvinowens@fb.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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@sergey-senozhatsky @pmladek
sergey-senozhatsky authored and pmladek committed Feb 8, 2017
1 parent 8b1742c commit de6fcbd
Showing 1 changed file with 65 additions and 38 deletions.
103 changes: 65 additions & 38 deletions kernel/printk/printk.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -370,6 +370,34 @@ __packed __aligned(4)
*/
DEFINE_RAW_SPINLOCK(logbuf_lock);

/*
* Helper macros to lock/unlock logbuf_lock and switch between
* printk-safe/unsafe modes.
*/
#define logbuf_lock_irq() \
do { \
printk_safe_enter_irq(); \
raw_spin_lock(&logbuf_lock); \
} while (0)

#define logbuf_unlock_irq() \
do { \
raw_spin_unlock(&logbuf_lock); \
printk_safe_exit_irq(); \
} while (0)

#define logbuf_lock_irqsave(flags) \
do { \
printk_safe_enter_irqsave(flags); \
raw_spin_lock(&logbuf_lock); \
} while (0)

#define logbuf_unlock_irqrestore(flags) \
do { \
raw_spin_unlock(&logbuf_lock); \
printk_safe_exit_irqrestore(flags); \
} while (0)

#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* the next printk record to read by syslog(READ) or /proc/kmsg */
Expand Down Expand Up @@ -801,28 +829,29 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
ret = mutex_lock_interruptible(&user->lock);
if (ret)
return ret;
raw_spin_lock_irq(&logbuf_lock);

logbuf_lock_irq();
while (user->seq == log_next_seq) {
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
goto out;
}

raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
ret = wait_event_interruptible(log_wait,
user->seq != log_next_seq);
if (ret)
goto out;
raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
}

if (user->seq < log_first_seq) {
/* our last seen message is gone, return error and reset */
user->idx = log_first_idx;
user->seq = log_first_seq;
ret = -EPIPE;
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
goto out;
}

Expand All @@ -835,7 +864,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,

user->idx = log_next(user->idx);
user->seq++;
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();

if (len > count) {
ret = -EINVAL;
Expand All @@ -862,7 +891,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
if (offset)
return -ESPIPE;

raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
switch (whence) {
case SEEK_SET:
/* the first record */
Expand All @@ -886,7 +915,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
default:
ret = -EINVAL;
}
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
return ret;
}

Expand All @@ -900,15 +929,15 @@ static unsigned int devkmsg_poll(struct file *file, poll_table *wait)

poll_wait(file, &log_wait, wait);

raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
if (user->seq < log_next_seq) {
/* return error when data has vanished underneath us */
if (user->seq < log_first_seq)
ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
else
ret = POLLIN|POLLRDNORM;
}
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();

return ret;
}
Expand Down Expand Up @@ -938,10 +967,10 @@ static int devkmsg_open(struct inode *inode, struct file *file)

mutex_init(&user->lock);

raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
user->idx = log_first_idx;
user->seq = log_first_seq;
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();

file->private_data = user;
return 0;
Expand Down Expand Up @@ -1083,13 +1112,13 @@ void __init setup_log_buf(int early)
return;
}

raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
log_buf_len = new_log_buf_len;
log_buf = new_log_buf;
new_log_buf_len = 0;
free = __LOG_BUF_LEN - log_next_idx;
memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);

pr_info("log_buf_len: %d bytes\n", log_buf_len);
pr_info("early log buf free: %d(%d%%)\n",
Expand Down Expand Up @@ -1267,15 +1296,15 @@ static int syslog_print(char __user *buf, int size)
size_t n;
size_t skip;

raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
if (syslog_seq < log_first_seq) {
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
syslog_partial = 0;
}
if (syslog_seq == log_next_seq) {
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
break;
}

Expand All @@ -1294,7 +1323,7 @@ static int syslog_print(char __user *buf, int size)
syslog_partial += n;
} else
n = 0;
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();

if (!n)
break;
Expand Down Expand Up @@ -1323,7 +1352,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
if (!text)
return -ENOMEM;

raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
if (buf) {
u64 next_seq;
u64 seq;
Expand Down Expand Up @@ -1371,12 +1400,12 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
idx = log_next(idx);
seq++;

raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
if (copy_to_user(buf + len, text, textlen))
len = -EFAULT;
else
len += textlen;
raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();

if (seq < log_first_seq) {
/* messages are gone, move to next one */
Expand All @@ -1390,7 +1419,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
clear_seq = log_next_seq;
clear_idx = log_next_idx;
}
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();

kfree(text);
return len;
Expand Down Expand Up @@ -1477,7 +1506,7 @@ int do_syslog(int type, char __user *buf, int len, int source)
break;
/* Number of chars in the log buffer */
case SYSLOG_ACTION_SIZE_UNREAD:
raw_spin_lock_irq(&logbuf_lock);
logbuf_lock_irq();
if (syslog_seq < log_first_seq) {
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
Expand Down Expand Up @@ -1505,7 +1534,7 @@ int do_syslog(int type, char __user *buf, int len, int source)
}
error -= syslog_partial;
}
raw_spin_unlock_irq(&logbuf_lock);
logbuf_unlock_irq();
break;
/* Size of the log buffer */
case SYSLOG_ACTION_SIZE_BUFFER:
Expand Down Expand Up @@ -1682,9 +1711,8 @@ asmlinkage int vprintk_emit(int facility, int level,
boot_delay_msec(level);
printk_delay();

printk_safe_enter_irqsave(flags);
/* This stops the holder of console_sem just where we want him */
raw_spin_lock(&logbuf_lock);
logbuf_lock_irqsave(flags);
/*
* The printf needs to come first; we need the syslog
* prefix which might be passed-in as a parameter.
Expand Down Expand Up @@ -1727,8 +1755,7 @@ asmlinkage int vprintk_emit(int facility, int level,

printed_len += log_output(facility, level, lflags, dict, dictlen, text, text_len);

raw_spin_unlock(&logbuf_lock);
printk_safe_exit_irqrestore(flags);
logbuf_unlock_irqrestore(flags);

/* If called from the scheduler, we can not call up(). */
if (!in_sched) {
Expand Down Expand Up @@ -2501,10 +2528,10 @@ void register_console(struct console *newcon)
* console_unlock(); will print out the buffered messages
* for us.
*/
raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);
/*
* We're about to replay the log buffer. Only do this to the
* just-registered console to avoid excessive message spam to
Expand Down Expand Up @@ -2803,12 +2830,12 @@ void kmsg_dump(enum kmsg_dump_reason reason)
/* initialize iterator with data about the stored records */
dumper->active = true;

raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
dumper->cur_seq = clear_seq;
dumper->cur_idx = clear_idx;
dumper->next_seq = log_next_seq;
dumper->next_idx = log_next_idx;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);

/* invoke dumper which will iterate over records */
dumper->dump(dumper, reason);
Expand Down Expand Up @@ -2893,9 +2920,9 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
unsigned long flags;
bool ret;

raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);

return ret;
}
Expand Down Expand Up @@ -2934,7 +2961,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
if (!dumper->active)
goto out;

raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
if (dumper->cur_seq < log_first_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = log_first_seq;
Expand All @@ -2943,7 +2970,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,

/* last entry */
if (dumper->cur_seq >= dumper->next_seq) {
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);
goto out;
}

Expand Down Expand Up @@ -2985,7 +3012,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
dumper->next_seq = next_seq;
dumper->next_idx = next_idx;
ret = true;
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);
out:
if (len)
*len = l;
Expand Down Expand Up @@ -3023,9 +3050,9 @@ void kmsg_dump_rewind(struct kmsg_dumper *dumper)
{
unsigned long flags;

raw_spin_lock_irqsave(&logbuf_lock, flags);
logbuf_lock_irqsave(flags);
kmsg_dump_rewind_nolock(dumper);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
logbuf_unlock_irqrestore(flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);

Expand Down

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