[CRIU] [PATCH v6] Printout early log messages

[Andrei Vagin]

Applied, thanks!

On Wed, Jan 09, 2019 at 01:11:12PM +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.
> 
> Improved-by: Andrei Vagin <avagin at gmail.com>
> Signed-off-by: Adrian Reber <areber at redhat.com>
> ---
>  criu/log.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 101 insertions(+)
> 
> diff --git a/criu/log.c b/criu/log.c
> index a268ab8..060d1ee 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;
>  /*
> @@ -155,6 +165,45 @@ static void print_versions(void)
>  		buf.release, buf.version, buf.machine);
>  }
>  
> +struct early_log_hdr {
> +	uint16_t level;
> +	uint16_t len;
> +};
> +
> +static void flush_early_log_buffer(int fd)
> +{
> +	unsigned int pos = 0;
> +	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.
> +		 */
> +		struct early_log_hdr *hdr = (void *)early_log_buffer + pos;
> +		pos += sizeof(hdr);
> +		if (hdr->level <= current_loglevel) {
> +			size_t size = 0;
> +			while (size < hdr->len) {
> +				ret = write(fd, early_log_buffer + pos + size,
> +						hdr->len - size);
> +				if (ret <= 0)
> +					break;
> +				size += ret;
> +			}
> +		}
> +		pos += hdr->len;
> +	}
> +	if (early_log_buf_off)
> +		pr_warn("The early log isn't empty\n");
> +	early_log_buf_off = 0;
> +}
> +
>  int log_init(const char *output)
>  {
>  	int new_logfd, fd;
> @@ -186,6 +235,14 @@ int log_init(const char *output)
>  	if (fd < 0)
>  		goto err;
>  
> +	init_done = 1;
> +
> +	/*
> +	 * Once logging is setup this write out all early log messages.
> +	 * Only those messages which have to correct log level are printed.
> +	 */
> +	flush_early_log_buffer(fd);
> +
>  	print_versions();
>  
>  	return 0;
> @@ -258,6 +315,41 @@ unsigned int log_get_loglevel(void)
>  	return current_loglevel;
>  }
>  
> +static void early_vprint(const char *format, unsigned int loglevel, va_list params)
> +{
> +	unsigned int log_size = 0;
> +	struct early_log_hdr *hdr;
> +
> +	if (early_log_buf_off >= EARLY_LOG_BUF_LEN)
> +		return;
> +
> +	/* Save loglevel */
> +
> +	hdr = (void *)early_log_buffer + early_log_buf_off;
> +	hdr->level  = loglevel;
> +	/* Skip the log entry size */
> +	early_log_buf_off += sizeof(hdr);
> +	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) ");
> +	}
> +
> +	log_size += vsnprintf(early_log_buffer + early_log_buf_off + log_size,
> +			sizeof(early_log_buffer) - early_log_buf_off - log_size,
> +			format, params);
> +
> +	/* Save log entry size */
> +	hdr->len = log_size;
> +	early_log_buf_off += log_size;
> +}
> +
>  void vprint_on_level(unsigned int loglevel, const char *format, va_list params)
>  {
>  	int fd, size, ret, off = 0;
> @@ -267,6 +359,14 @@ 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();
> @@ -284,6 +384,7 @@ 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
>