On Tue 2020-09-22 17:44:12, John Ogness wrote: > After copying all records to the dynamic ringbuffer, setup_log_buf() > checks to see if any records were dropped during the switch. However, > it needs to check before enabling interrupts since new records could > arrive in an interrupt, thus causing setup_log_buf() to erroneously > think that it had dropped messages.
Have you seen the problem, please? > Signed-off-by: John Ogness <[email protected]> > --- > kernel/printk/printk.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index 1fe3d0cb2fe0..00bc1fce3299 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -1181,12 +1181,12 @@ void __init setup_log_buf(int early) > */ > prb = &printk_rb_dynamic; > > + seq = prb_next_seq(&printk_rb_static) - seq; > + > logbuf_unlock_irqrestore(flags); > > - if (seq != prb_next_seq(&printk_rb_static)) { I can't see how these two values could get modified after enabling interrupts. + @seq is set in the for-cycle before the interrupts are enabled. + @prb is updated before the interrupts are enabled. So that the static buffer should not longer be used after that. > - pr_err("dropped %llu messages\n", > - prb_next_seq(&printk_rb_static) - seq); > - } > + if (seq) > + pr_err("dropped %llu messages\n", seq); > > pr_info("log_buf_len: %u bytes\n", log_buf_len); > pr_info("early log buf free: %u(%u%%)\n", Best Regards, Petr
