On Thu 2020-06-18 16:55:19, John Ogness wrote:
> Replace the existing ringbuffer usage and implementation with
> lockless ringbuffer usage. Even though the new ringbuffer does not
> require locking, all existing locking is left in place. Therefore,
> this change is purely replacing the underlining ringbuffer.
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1609,11 +1633,15 @@ 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:
> + if (source != SYSLOG_FROM_PROC) {
> + text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
> + if (!text)
> + return -ENOMEM;
The buffer is needed only to count lines to count the size of
added prefixes. Could we use the new prb_read_valid_info() that
allows to get the number of lines without actually reading the buffer?
> +
> + }
> logbuf_lock_irq();
> - if (syslog_seq < log_first_seq) {
> + if (syslog_seq < prb_first_seq(prb)) {
> /* messages are gone, move to first one */
> - syslog_seq = log_first_seq;
> - syslog_idx = log_first_idx;
> + syslog_seq = prb_first_seq(prb);
> syslog_partial = 0;
> }
> if (source == SYSLOG_FROM_PROC) {
Best Regards,
Petr
