On Thu 2020-07-09 12:59:06, Petr Mladek wrote: > 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; I though more about it. IMHO, it will be better to modify prb_first_seq() to do the same cycle as prb_next_seq() and return seq number of the first valid entry. IMHO, basically any caller in printk.c expects this behavior. For example, devkmsg user would expect reading valid entry after doing SEEK_SET. I would also expect to get valid record right after opening devkmsg, etc. The current prb_first_seq() is needed only _prb_read_valid(). For, this I would rename the original function to prb_tail_seq(). Best Regards, Petr _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
