On Thu 2020-07-09 12:20:35, John Ogness wrote: > On 2020-07-09, Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> wrote: > > On (20/07/09 15:14), kernel test robot wrote: > > [..] > > > > Took me a while to find the FAIL-ed test: > > > >> kmsg01.c:393: INFO: TEST: read returns EPIPE when messages get overwritten > >> kmsg01.c:398: INFO: first seqno: 0 > >> kmsg01.c:411: INFO: first seqno now: 881 > >> kmsg01.c:425: FAIL: read returned: 77: SUCCESS (0) > > > > So this is seq number related > > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/logging/kmsg/kmsg01.c#L383 > > Excellent test. > > Since the messages are above the expected average size, the dataring is > wrapping before the descriptor ring. This means that the initial > descriptors are still there, but their data is gone. Initially I would > generate an EPIPE for this, but it was changed. Here is the thread [0] > we had about this. I see. IMHO, the following should do the job. The check is done only when the above prb_read_valid() succeeded. Therefore the printk_record has to include a valid value. And it must be the first valid record when some messages were lost. diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 62fc1abd9c4d..5d4760b5c671 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -775,9 +775,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, logbuf_lock_irq(); } - if (user->seq < prb_first_seq(prb)) { + if (user->seq < r->info->seq) { /* our last seen message is gone, return error and reset */ - user->seq = prb_first_seq(prb); + user->seq = r->info->seq; ret = -EPIPE; logbuf_unlock_irq(); goto out; Best Regards, Petr _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
