[CRIU] [PATCH v4 1/3] Printout early log messages

[Andrei Vagin]

On Thu, Dec 13, 2018 at 08:08:16AM +0000, Adrian Reber wrote:
> From: Adrian Reber <areber at redhat.com>
> 
> Up until now any pr_* logging command (except pr_msg) was lost if
> logging has not been set up (log_init()).
> 
> To make sure not logging messages are lost, vprint_on_level() now writes
> all messages (except LOG_MSG) to a temporary buffer which is written
> to the logging FD once that is set up.
> 
> Related: https://github.com/checkpoint-restore/criu/issues/578
> 
> Signed-off-by: Adrian Reber <areber at redhat.com>
> ---
>  criu/log.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 94 insertions(+)
> 
> diff --git a/criu/log.c b/criu/log.c
> index a268ab8..398c443 100644
> --- a/criu/log.c
> +++ b/criu/log.c
> @@ -31,11 +31,21 @@
>  /* Enable timestamps if verbosity is increased from default */
>  #define LOG_TIMESTAMP		(DEFAULT_LOGLEVEL + 1)
>  #define LOG_BUF_LEN		(8*1024)
> +#define EARLY_LOG_BUF_LEN	1024
>  
>  static unsigned int current_loglevel = DEFAULT_LOGLEVEL;
>  
>  static char buffer[LOG_BUF_LEN];
>  static char buf_off = 0;
> +/*
> + * The early_log_buffer is used to store log messages before
> + * logging is set up to make sure no logs are lost.
> + */
> +static char early_log_buffer[EARLY_LOG_BUF_LEN];
> +static unsigned int early_log_buf_off = 0;
> +
> +/* If this is 0 the logging has not been set up yet. */
> +static int init_done = 0;
>  
>  static struct timeval start;
>  /*
> @@ -186,6 +196,8 @@ int log_init(const char *output)
>  	if (fd < 0)
>  		goto err;
>  
> +	init_done = 1;
> +
>  	print_versions();
>  
>  	return 0;
> @@ -258,6 +270,72 @@ unsigned int log_get_loglevel(void)
>  	return current_loglevel;
>  }
>  
> +void early_vprint(const char *format, unsigned int loglevel, va_list params)
> +{
> +	unsigned int log_size = 0;
> +
> +	if (early_log_buf_off >= EARLY_LOG_BUF_LEN)
> +		return;
> +
> +	/* Save loglevel */
> +	early_log_buffer[early_log_buf_off++] = loglevel;

I would say that early_log has to contain only errors

> +	/* Skip the log entry size */
> +	early_log_buf_off += sizeof(unsigned int);
> +	if (loglevel >= LOG_TIMESTAMP) {
> +		/*
> +		 * If logging is not yet setup we just write zeros
> +		 * instead of a real timestamp. This way we can
> +		 * keep the same format as the other messages on
> +		 * log levels with timestamps (>=LOG_TIMESTAMP).
> +		 */
> +		log_size  = snprintf(early_log_buffer + early_log_buf_off, sizeof early_log_buffer - early_log_buf_off, "(00.000000) ");

This line is too long


		early_log_buf_off += log_size;

> +	}
> +
> +	log_size += vsnprintf(early_log_buffer + early_log_buf_off + log_size, sizeof early_log_buffer - early_log_buf_off - log_size, format, params);

This line is too long

sizeof(early_log_buffer), otherwise it is hard to read

> +	/* Save log entry size */
> +	memcpy(early_log_buffer + (early_log_buf_off - sizeof(unsigned int)), &log_size, sizeof(unsigned int));
> +	early_log_buf_off += log_size;
> +}
> +
> +void flush_early_log_buffer(int fd)
> +{
> +	unsigned int log_size;
> +	unsigned int pos = 0;
> +	int tmp_log_level;
> +	int size;
> +	int ret;
> +
> +	while (pos < early_log_buf_off) {
> +		/*
> +		 * The early_log_buffer contains all messages written
> +		 * before logging was set up. We only want to print
> +		 * out messages which correspond to the requested
> +		 * log_level. Therefore the early_log_buffer also contains
> +		 * the log_level and the size. This writes one messages,
> +		 * depending on the log_level, to the logging fd. Start
> +		 * with reading the log_level.
> +		 */
> +		tmp_log_level = early_log_buffer[pos++];
> +		/* Read out log message size */
> +		memcpy(&log_size, early_log_buffer + pos, sizeof(unsigned int));
> +		pos += sizeof(unsigned int);
> +		size = 0;
> +		if (tmp_log_level <= current_loglevel) {
> +			while (size < log_size) {
> +				ret = write(fd, early_log_buffer + pos + size, log_size - size);
> +				if (ret <= 0)
> +					break;
> +				size += ret;
> +			}
> +		} else {
> +			size += log_size;
> +		}
> +		pos += size;
> +	}
> +	early_log_buf_off = 0;
> +
> +}
> +
>  void vprint_on_level(unsigned int loglevel, const char *format, va_list params)
>  {
>  	int fd, size, ret, off = 0;
> @@ -267,6 +345,14 @@ void vprint_on_level(unsigned int loglevel, const char *format, va_list params)
>  		fd = STDOUT_FILENO;
>  		off = buf_off; /* skip dangling timestamp */
>  	} else {
> +		/*
> +		 * If logging has not yet been initialized (init_done == 0)
> +		 * make sure all messages are written to the early_log_buffer.
> +		 */
> +		if (!init_done) {
> +			early_vprint(format, loglevel, params);
> +			return;
> +		}
>  		if (loglevel > current_loglevel)
>  			return;
>  		fd = log_get_fd();
> @@ -274,6 +360,13 @@ void vprint_on_level(unsigned int loglevel, const char *format, va_list params)
>  			print_ts();
>  	}
>  
> +	/*
> +	 * Once logging is setup this write out all early log messages.
> +	 * Only those messages which have to correct log level are printed.
> +	 */
> +	if (early_log_buf_off && init_done)
> +		flush_early_log_buffer(fd);

I don't understand why it is here. Why is it not in log_init()?

> +
>  	size  = vsnprintf(buffer + buf_off, sizeof buffer - buf_off, format, params);
>  	size += buf_off;
>  
> @@ -284,6 +377,7 @@ void vprint_on_level(unsigned int loglevel, const char *format, va_list params)
>  		off += ret;
>  	}
>  
> +	/* This is missing for messages in the early_log_buffer. */
>  	if (loglevel == LOG_ERROR)
>  		log_note_err(buffer + buf_off);
>  
> -- 
> 1.8.3.1
>