Messages in this thread | | | Date | Thu, 25 Jun 2020 17:20:42 +0200 | From | Petr Mladek <> | Subject | syslog size unread: was: [PATCH v3 3/3] printk: use the lockless ringbuffer |
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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
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