On 8/27/19 4:16 PM, Brendan Higgins wrote:
On Tue, Aug 27, 2019 at 3:00 PM shuah shuah@kernel.org wrote:
On 8/27/19 3:36 PM, Brendan Higgins wrote:
On Tue, Aug 27, 2019 at 2:09 PM Brendan Higgins brendanhiggins@google.com wrote:
On Tue, Aug 27, 2019 at 2:03 PM Brendan Higgins brendanhiggins@google.com wrote:
On Tue, Aug 27, 2019 at 1:21 PM shuah shuah@kernel.org wrote:
On 8/27/19 11:49 AM, Brendan Higgins wrote: > Previously KUnit assumed that printk would always be present, which is > not a valid assumption to make. Fix that by ifdefing out functions which > directly depend on printk core functions similar to what dev_printk > does. > > Reported-by: Randy Dunlap rdunlap@infradead.org > Link: https://lore.kernel.org/linux-kselftest/0352fae9-564f-4a97-715a-fabe016259df... > Cc: Stephen Rothwell sfr@canb.auug.org.au > Signed-off-by: Brendan Higgins brendanhiggins@google.com > --- > include/kunit/test.h | 7 +++++++ > kunit/test.c | 41 ++++++++++++++++++++++++----------------- > 2 files changed, 31 insertions(+), 17 deletions(-) > > diff --git a/include/kunit/test.h b/include/kunit/test.h > index 8b7eb03d4971..339af5f95c4a 100644 > --- a/include/kunit/test.h > +++ b/include/kunit/test.h > @@ -339,9 +339,16 @@ static inline void *kunit_kzalloc(struct kunit *test, size_t size, gfp_t gfp)
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Okay after reviewing this, I am not sure why you need to do all this.
Why can't you just change the root function that throws the warn:
static int kunit_vprintk_emit(int level, const char *fmt, va_list args){ return vprintk_emit(0, level, NULL, 0, fmt, args); }
You aren'r really doing anything extra here, other than calling vprintk_emit()
Yeah, I did that a while ago. I think it was a combination of trying to avoid an extra layer of adding and then removing the log level, and that's what dev_printk and friends did.
But I think you are probably right. It's a lot of maintenance overhead to get rid of that. Probably best to just use what the printk people have.
Unless I am missing something, can't you solve this problem by including printk.h and let it handle the !CONFIG_PRINTK case?
Randy, I hope you don't mind, but I am going to ask you to re-ack my next revision since it basically addresses the problem in a totally different way.
Actually, scratch that. Checkpatch doesn't like me calling printk without using a KERN_<LEVEL>.
Now that I am thinking back to when I wrote this. I think it also might not like using a dynamic KERN_<LEVEL> either (printk("%s my message", KERN_INFO)).
I am going to have to do some more investigation.
Alright, I am pretty sure it is safe to do printk("%smessage", KERN_<LEVEL>);
Looking at the printk implementation, it appears to do the format before it checks the log level:
https://elixir.bootlin.com/linux/v5.2.10/source/kernel/printk/printk.c#L1907
So I am pretty sure we can do it either with the vprintk_emit or with printk.
Let me see if we are on the same page first. I am asking if you can just include printk.h for vprintk_emit() define for both CONFIG_PRINTK and !CONFIG_PRINTK cases.
Ah sorry, I misunderstood you.
No, that doesn't work. I tried including linux/printk.h, and I get the same error.
The reason for this is that vprintk_emit() is only defined when CONFIG_PRINTK=y:
This is the real problem here. printk.h defines several for !CONFIG_PRINTK case.
https://elixir.bootlin.com/linux/latest/ident/vprintk_emit
I am not asking you to use printk() in place of vprintk_emit(). It is perfectly fine to use vprintk_emit()
Okay, cool.
So it appears that we have to weigh the following trade-offs:
Using vprintk_emit:
Pros:
- That's what dev_printk uses.
Not sure what you mean by this. I am suggesting if you can just call vprintk_emit() and include printk.h and not have to ifdef around all the other callers of kunit_vprintk_emit()
Oh, I was just saying that I heavily based my implementation of kunit_printk on dev_printk. So I have a high degree of confidence that it is okay to use it the way that I am using it.
Yes. There is the other issue of why do you need the complexity of having kunit_vprintk_emit() at all.
Right, and the problem with the alternative, is there is no good kernel API for logging with the log level set dynamically. printk prefers to have it as a string prefix on the format string, but I cannot do that because I need to add my own prefix to the format string.
So, I guess I should just go ahead and address the earlier comments on this patch?
So what does your code do in the case of !CONFIG_PRINTK. From my read of it, it returns 0 from kunit_printk_emit(0 from my read of it. What I am saying is this is a lot of indirection instead of fixing the leaf function which is kunit_vprintk_emit().
+#else /* CONFIG_PRINTK */ +static inline int kunit_printk_emit(int level, const char *fmt, ...) +{ + return 0; +} +#endif /* CONFIG_PRINTK */
Does the following work?
#if defined CONFIG_PRINTK static int kunit_vprintk_emit(int level, const char *fmt, va_list args) { return vprintk_emit(0, level, NULL, 0, fmt, args); } #else static int kunit_vprintk_emit(int level, const char *fmt, va_list args) { return 0; } #endif
I think the real problem is in the printk.h with its missing define for vprintk_emit() for !CONFIG_PRINTK case. There seem to only one call for this in drivers/base/core.c in CONFIG_PRINTK path. Unless I am totally missing some context for why there is no stub for vprintk_emit() for !CONFIG_PRINTK case
thanks, -- Shuah