On 2014.09.20 at 11:32 -0400, Steven Rostedt wrote: > On Sat, 20 Sep 2014 07:12:24 +0200 > Jan Kara <j...@suse.cz> wrote: > > > On Thu 18-09-14 19:34:14, Peter Zijlstra wrote: > > > On Wed, Sep 17, 2014 at 08:31:35PM -0400, Steven Rostedt wrote: > > > > I totally didn't get what you wrote. > > > > > > :-) > > > > > > > We don't want to know if it got delayed, then the patch to remove that > > > > print seems correct. > > > > > > Why would you not want to know that? Also was that the actual argument? > > > Lemme go check the earlier emails -- I cannot find that argument in the > > > first few emails. > > Well, so what gets delayed is printing from kernel buffer to console. > > So this is the same as when you do printk() when console lock is taken by > > someone else. So it seems a bit strange to prepend [delayed] in some cases > > and not in others. > > > > Another question is what the [delayed] prefix would be useful for? If the > > message eventually gets printed to console I don't see why you would care > > it was printed few ms after it entered the kernel buffer (after all the > > time stamp before the line will be the time when it entered the kernel > > buffer). And if the kernel crashes in such a way that the message doesn't > > get printed, then bad luck but prefix in the kernel log buffer isn't going > > to make that any better :) > > > > This all feels like bikeshedding, I don't deeply care what gets done but I > > wanted to point out I don't really see a use for [delayed]... > > > > I pretty much agree with this assessment. I don't really care if > there's a "[delayed]" message or not. I now agree that it isn't really > that useful. Now what I do care about is that there's a bug with the > current code, and the non bikeshed argument is how to fix this bug. > > The bug is that there's users of printk_deferred() that use KERN_WARN > in the format. This ends up showing "[delayed]<whacky-characters> > message". The fix needs to remove those whacky characters. > > There's three ways to fix this bug. > > 1) change printk() to check for whacky characters before adding > "[delayed]" and either move them before it or remove them all together. > > 2) change all users of printk_deferred() to not add the KERN_WARN. > > 3) just get rid of adding the "[delayed]" message and make printk() > itself a bit cleaner. > > I'm leaning towards #3 as I don't see the usefulness of that > "[delayed]" message if there's other cases that can also delay printk. > Remember, the code has been changed since the delayed message was added > to make sure that the printk_deferred() message gets into the printk > message in sequence of other printk's happening. The original way (when > the "delayed" message was added) used its own buffer and would write to > the log buffer at a later time, where the printk_deferred() could > actually come out of sequence with other printk()s, and the "[delayed]" > message would be useful for that case. But it's not useful anymore. > > #1 of above will just makes printk more complex, and being such a > critical function which is already complex enough, I would like to not > do so. > > #2 can fix the issue for now, until someone else adds a > printk_deferred() with another KERN_WARN. Worse yet, someone may add > one of the other KERN_* log levels and it will be ignored.
There are already two "printk_deferred(KERN_ERR" in kernel/time/ntp.c, that get currently transformed to KERN_WARN. > Getting beyond the bikeshedding, there's a real bug that should be > fixed. We just need to figure out what's the best way to do so. I agree that 3) is the best solution. Feel free to just add the description of why it now makes sense to the patch. -- Markus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
