printk: remove logbuf_lock
Since the ringbuffer is lockless, there is no need for it to be protected by @logbuf_lock. Remove @logbuf_lock. @console_seq, @exclusive_console_stop_seq, @console_dropped are protected by @console_lock. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210303101528.29901-14-john.ogness@linutronix.de
This commit is contained in:
John Ogness
Petr Mladek
Родитель
f9f3f02db9
Коммит
996e966640
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@ -12,8 +12,6 @@
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#define PRINTK_NMI_CONTEXT_OFFSET 0x010000000
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extern raw_spinlock_t logbuf_lock;
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__printf(4, 0)
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int vprintk_store(int facility, int level,
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const struct dev_printk_info *dev_info,
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@ -59,7 +57,7 @@ void defer_console_output(void);
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__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
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/*
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* In !PRINTK builds we still export logbuf_lock spin_lock, console_sem
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* In !PRINTK builds we still export console_sem
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* semaphore and some of console functions (console_unlock()/etc.), so
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* printk-safe must preserve the existing local IRQ guarantees.
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*/
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@ -355,41 +355,6 @@ enum log_flags {
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LOG_CONT = 8, /* text is a fragment of a continuation line */
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};
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/*
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* The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
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* within the scheduler's rq lock. It must be released before calling
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* console_unlock() or anything else that might wake up a process.
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*/
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DEFINE_RAW_SPINLOCK(logbuf_lock);
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/*
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* Helper macros to lock/unlock logbuf_lock and switch between
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* printk-safe/unsafe modes.
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*/
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#define logbuf_lock_irq() \
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do { \
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printk_safe_enter_irq(); \
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raw_spin_lock(&logbuf_lock); \
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} while (0)
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#define logbuf_unlock_irq() \
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do { \
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raw_spin_unlock(&logbuf_lock); \
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printk_safe_exit_irq(); \
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} while (0)
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#define logbuf_lock_irqsave(flags) \
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do { \
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printk_safe_enter_irqsave(flags); \
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raw_spin_lock(&logbuf_lock); \
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} while (0)
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#define logbuf_unlock_irqrestore(flags) \
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do { \
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raw_spin_unlock(&logbuf_lock); \
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printk_safe_exit_irqrestore(flags); \
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} while (0)
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/* syslog_lock protects syslog_* variables and write access to clear_seq. */
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static DEFINE_RAW_SPINLOCK(syslog_lock);
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@ -401,6 +366,7 @@ static u64 syslog_seq;
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static size_t syslog_partial;
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static bool syslog_time;
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/* All 3 protected by @console_sem. */
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/* the next printk record to write to the console */
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static u64 console_seq;
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static u64 exclusive_console_stop_seq;
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@ -766,27 +732,27 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
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if (ret)
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return ret;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) {
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if (file->f_flags & O_NONBLOCK) {
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ret = -EAGAIN;
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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goto out;
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}
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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ret = wait_event_interruptible(log_wait,
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prb_read_valid(prb, atomic64_read(&user->seq), r));
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if (ret)
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goto out;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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}
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if (r->info->seq != atomic64_read(&user->seq)) {
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/* our last seen message is gone, return error and reset */
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atomic64_set(&user->seq, r->info->seq);
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ret = -EPIPE;
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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goto out;
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}
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@ -796,7 +762,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
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&r->info->dev_info);
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atomic64_set(&user->seq, r->info->seq + 1);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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if (len > count) {
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ret = -EINVAL;
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@ -831,7 +797,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
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if (offset)
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return -ESPIPE;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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switch (whence) {
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case SEEK_SET:
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/* the first record */
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@ -852,7 +818,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
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default:
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ret = -EINVAL;
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}
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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return ret;
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}
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@ -867,7 +833,7 @@ static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
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poll_wait(file, &log_wait, wait);
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logbuf_lock_irq();
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printk_safe_enter_irq();
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if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) {
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/* return error when data has vanished underneath us */
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if (info.seq != atomic64_read(&user->seq))
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@ -875,7 +841,7 @@ static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
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else
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ret = EPOLLIN|EPOLLRDNORM;
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}
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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return ret;
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}
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@ -908,9 +874,9 @@ static int devkmsg_open(struct inode *inode, struct file *file)
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prb_rec_init_rd(&user->record, &user->info,
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&user->text_buf[0], sizeof(user->text_buf));
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logbuf_lock_irq();
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printk_safe_enter_irq();
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atomic64_set(&user->seq, prb_first_valid_seq(prb));
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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file->private_data = user;
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return 0;
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@ -1532,11 +1498,11 @@ static int syslog_print(char __user *buf, int size)
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size_t n;
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size_t skip;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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raw_spin_lock(&syslog_lock);
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if (!prb_read_valid(prb, syslog_seq, &r)) {
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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break;
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}
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if (r.info->seq != syslog_seq) {
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@ -1566,7 +1532,7 @@ static int syslog_print(char __user *buf, int size)
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} else
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n = 0;
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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if (!n)
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break;
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@ -1600,7 +1566,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
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return -ENOMEM;
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time = printk_time;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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/*
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* Find first record that fits, including all following records,
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* into the user-provided buffer for this dump.
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@ -1621,12 +1587,12 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
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break;
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}
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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if (copy_to_user(buf + len, text, textlen))
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len = -EFAULT;
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else
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len += textlen;
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logbuf_lock_irq();
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printk_safe_enter_irq();
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if (len < 0)
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break;
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@ -1637,7 +1603,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
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latched_seq_write(&clear_seq, seq);
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raw_spin_unlock(&syslog_lock);
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}
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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kfree(text);
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return len;
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@ -1645,11 +1611,11 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
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static void syslog_clear(void)
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{
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logbuf_lock_irq();
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printk_safe_enter_irq();
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raw_spin_lock(&syslog_lock);
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latched_seq_write(&clear_seq, prb_next_seq(prb));
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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}
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/* Return a consistent copy of @syslog_seq. */
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@ -1737,12 +1703,12 @@ int do_syslog(int type, char __user *buf, int len, int source)
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break;
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/* Number of chars in the log buffer */
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case SYSLOG_ACTION_SIZE_UNREAD:
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logbuf_lock_irq();
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printk_safe_enter_irq();
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raw_spin_lock(&syslog_lock);
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if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) {
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/* No unread messages. */
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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return 0;
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}
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if (info.seq != syslog_seq) {
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@ -1771,7 +1737,7 @@ int do_syslog(int type, char __user *buf, int len, int source)
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error -= syslog_partial;
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}
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irq();
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printk_safe_exit_irq();
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break;
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/* Size of the log buffer */
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case SYSLOG_ACTION_SIZE_BUFFER:
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@ -2627,7 +2593,6 @@ again:
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size_t len;
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printk_safe_enter_irqsave(flags);
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raw_spin_lock(&logbuf_lock);
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skip:
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if (!prb_read_valid(prb, console_seq, &r))
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break;
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@ -2671,7 +2636,6 @@ skip:
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console_msg_format & MSG_FORMAT_SYSLOG,
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printk_time);
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console_seq++;
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raw_spin_unlock(&logbuf_lock);
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/*
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* While actively printing out messages, if another printk()
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@ -2698,8 +2662,6 @@ skip:
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console_locked = 0;
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raw_spin_unlock(&logbuf_lock);
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up_console_sem();
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/*
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@ -2708,9 +2670,7 @@ skip:
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* there's a new owner and the console_unlock() from them will do the
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* flush, no worries.
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*/
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raw_spin_lock(&logbuf_lock);
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retry = prb_read_valid(prb, console_seq, NULL);
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raw_spin_unlock(&logbuf_lock);
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printk_safe_exit_irqrestore(flags);
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if (retry && console_trylock())
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@ -2777,9 +2737,9 @@ void console_flush_on_panic(enum con_flush_mode mode)
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if (mode == CONSOLE_REPLAY_ALL) {
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unsigned long flags;
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logbuf_lock_irqsave(flags);
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printk_safe_enter_irqsave(flags);
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console_seq = prb_first_valid_seq(prb);
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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}
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console_unlock();
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}
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@ -3008,7 +2968,7 @@ void register_console(struct console *newcon)
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* console_unlock(); will print out the buffered messages
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* for us.
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*/
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logbuf_lock_irqsave(flags);
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printk_safe_enter_irqsave(flags);
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/*
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* We're about to replay the log buffer. Only do this to the
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* just-registered console to avoid excessive message spam to
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@ -3026,7 +2986,7 @@ void register_console(struct console *newcon)
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console_seq = syslog_seq;
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raw_spin_unlock(&syslog_lock);
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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}
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console_unlock();
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console_sysfs_notify();
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@ -3492,9 +3452,9 @@ bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
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unsigned long flags;
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bool ret;
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logbuf_lock_irqsave(flags);
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printk_safe_enter_irqsave(flags);
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ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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return ret;
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}
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@ -3538,7 +3498,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
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if (iter->cur_seq < min_seq)
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iter->cur_seq = min_seq;
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logbuf_lock_irqsave(flags);
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printk_safe_enter_irqsave(flags);
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if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
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if (info.seq != iter->cur_seq) {
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/* messages are gone, move to first available one */
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@ -3548,7 +3508,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
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/* last entry */
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if (iter->cur_seq >= iter->next_seq) {
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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goto out;
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}
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@ -3582,7 +3542,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
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iter->next_seq = next_seq;
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ret = true;
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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out:
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if (len_out)
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*len_out = len;
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@ -3618,9 +3578,9 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
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{
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unsigned long flags;
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logbuf_lock_irqsave(flags);
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printk_safe_enter_irqsave(flags);
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kmsg_dump_rewind_nolock(iter);
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logbuf_unlock_irqrestore(flags);
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printk_safe_exit_irqrestore(flags);
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}
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EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
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@ -16,7 +16,7 @@
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#include "internal.h"
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/*
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* printk() could not take logbuf_lock in NMI context. Instead,
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* In NMI and safe mode, printk() avoids taking locks. Instead,
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* it uses an alternative implementation that temporary stores
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* the strings into a per-CPU buffer. The content of the buffer
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* is later flushed into the main ring buffer via IRQ work.
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@ -267,17 +267,9 @@ void printk_safe_flush(void)
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void printk_safe_flush_on_panic(void)
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{
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/*
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* Make sure that we could access the main ring buffer.
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* Make sure that we could access the safe buffers.
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* Do not risk a double release when more CPUs are up.
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*/
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if (raw_spin_is_locked(&logbuf_lock)) {
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if (num_online_cpus() > 1)
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return;
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debug_locks_off();
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raw_spin_lock_init(&logbuf_lock);
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}
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if (raw_spin_is_locked(&safe_read_lock)) {
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if (num_online_cpus() > 1)
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return;
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@ -319,9 +311,7 @@ void noinstr printk_nmi_exit(void)
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* reordering.
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*
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* It has effect only when called in NMI context. Then printk()
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* will try to store the messages into the main logbuf directly
|
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* and use the per-CPU buffers only as a fallback when the lock
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* is not available.
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* will store the messages into the main logbuf directly.
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*/
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void printk_nmi_direct_enter(void)
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{
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@ -376,20 +366,21 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
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#endif
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/*
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* Try to use the main logbuf even in NMI. But avoid calling console
|
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* Use the main logbuf even in NMI. But avoid calling console
|
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* drivers that might have their own locks.
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*/
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if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&
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raw_spin_trylock(&logbuf_lock)) {
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if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK)) {
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unsigned long flags;
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int len;
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printk_safe_enter_irqsave(flags);
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len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
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raw_spin_unlock(&logbuf_lock);
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printk_safe_exit_irqrestore(flags);
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defer_console_output();
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return len;
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}
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/* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */
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/* Use extra buffer in NMI. */
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if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
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return vprintk_nmi(fmt, args);
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