Date:   Fri, 30 Aug 2019 13:46:52 -0700
From:   Joe Perches <joe@...ches.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     shuah <shuah@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        kunit-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, frowand.list@...il.com,
        sboyd@...nel.org, pmladek@...e.com, sergey.senozhatsky@...il.com,
        rostedt@...dmis.org, Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v2] kunit: fix failure to build without printk

On Fri, 2019-08-30 at 11:38 -0700, Brendan Higgins wrote:
> On Thu, Aug 29, 2019 at 09:44:58PM -0700, Joe Perches wrote:
> > On Thu, 2019-08-29 at 11:01 -0600, shuah wrote:
> > > On 8/28/19 3:49 AM, Sergey Senozhatsky wrote:
> > > > On (08/28/19 02:31), Brendan Higgins wrote:
> > > > [..]
> > > > > Previously KUnit assumed that printk would always be present, which is
> > > > > not a valid assumption to make. Fix that by removing call to
> > > > > vprintk_emit, and calling printk directly.
> > > > > 
> > > > > Reported-by: Randy Dunlap <rdunlap@...radead.org>
> > > > > Link: https://lore.kernel.org/linux-kselftest/0352fae9-564f-4a97-715a-fabe016259df@kernel.org/T/#t
> > > > > Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> > > > > Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
> > > > > Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
> > > > 
> > > > [..]
> > > > 
> > > > > -static void kunit_vprintk(const struct kunit *test,
> > > > > -			  const char *level,
> > > > > -			  struct va_format *vaf)
> > > > > -{
> > > > > -	kunit_printk_emit(level[1] - '0', "\t# %s: %pV", test->name, vaf);
> > > > > -}
> > > > 
> > > > This patch looks good to me. I like the removal of recursive
> > > > vsprintf() (%pV).
> > > > 
> > > > 	-ss
> > > > 
> > > 
> > > Hi Sergey,
> > > 
> > > What are the guidelines for using printk(). I recall some discussion
> > > about not using printk(). I am seeing the following from checkpatch
> > > script:
> > > 
> > > 
> > > WARNING: Prefer [subsystem eg: netdev]_level([subsystem]dev, ... then 
> > > dev_level(dev, ... then pr_level(...  to printk(KERN_LEVEL ...
> > > #105: FILE: include/kunit/test.h:343:
> > > +	printk(KERN_LEVEL "\t# %s: " fmt, (test)->name, ##__VA_ARGS__)
> > > 
> > > 
> > > Is there supposed to be pr_level() - I can find dev_level()
> > > 
> > > cc'ing Joe Perches for his feedback on this message recommending
> > > pr_level() which isn't in 5.3.
> > 
> > I don't care for pr_level or KERN_LEVEL in a printk.
> 
> I don't think I follow, how does your version fix this?
> 
> > I think this is somewhat overly complicated.
> > 
> > I think I'd write it like:
> > ---
> >  include/kunit/test.h | 11 ++++-----
> >  kunit/test.c         | 69 ++++++++++++++++------------------------------------
> >  2 files changed, 26 insertions(+), 54 deletions(-)
> > 
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index 8b7eb03d4971..aa4abf0a22a5 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -339,9 +339,8 @@ static inline void *kunit_kzalloc(struct kunit *test, size_t size, gfp_t gfp)
> >  
> >  void kunit_cleanup(struct kunit *test);
> >  
> > -void __printf(3, 4) kunit_printk(const char *level,
> > -				 const struct kunit *test,
> > -				 const char *fmt, ...);
> > +__printf(2, 3)
> > +void kunit_printk(const struct kunit *test, const char *fmt, ...);
> >  
> >  /**
> >   * kunit_info() - Prints an INFO level message associated with @test.
> > @@ -353,7 +352,7 @@ void __printf(3, 4) kunit_printk(const char *level,
> >   * Takes a variable number of format parameters just like printk().
> >   */
> >  #define kunit_info(test, fmt, ...) \
> > -	kunit_printk(KERN_INFO, test, fmt, ##__VA_ARGS__)
> > +	kunit_printk(test, KERN_INFO fmt, ##__VA_ARGS__)
> >  
> >  /**
> >   * kunit_warn() - Prints a WARN level message associated with @test.
> > @@ -364,7 +363,7 @@ void __printf(3, 4) kunit_printk(const char *level,
> >   * Prints a warning level message.
> >   */
> >  #define kunit_warn(test, fmt, ...) \
> > -	kunit_printk(KERN_WARNING, test, fmt, ##__VA_ARGS__)
> > +	kunit_printk(test, KERN_WARNING fmt, ##__VA_ARGS__)
> >  
> >  /**
> >   * kunit_err() - Prints an ERROR level message associated with @test.
> > @@ -375,7 +374,7 @@ void __printf(3, 4) kunit_printk(const char *level,
> >   * Prints an error level message.
> >   */
> >  #define kunit_err(test, fmt, ...) \
> > -	kunit_printk(KERN_ERR, test, fmt, ##__VA_ARGS__)
> > +	kunit_printk(test, KERN_ERR fmt, ##__VA_ARGS__)
> >  
> >  /**
> >   * KUNIT_SUCCEED() - A no-op expectation. Only exists for code clarity.
> > diff --git a/kunit/test.c b/kunit/test.c
> > index b2ca9b94c353..ddb9bffb5a5d 100644
> > --- a/kunit/test.c
> > +++ b/kunit/test.c
> > @@ -16,40 +16,6 @@ static void kunit_set_failure(struct kunit *test)
> >  	WRITE_ONCE(test->success, false);
> >  }
> >  
> > -static int kunit_vprintk_emit(int level, const char *fmt, va_list args)
> > -{
> > -	return vprintk_emit(0, level, NULL, 0, fmt, args);
> > -}
> > -
> > -static int kunit_printk_emit(int level, const char *fmt, ...)
> > -{
> > -	va_list args;
> > -	int ret;
> > -
> > -	va_start(args, fmt);
> > -	ret = kunit_vprintk_emit(level, fmt, args);
> > -	va_end(args);
> > -
> > -	return ret;
> > -}
> > -
> > -static void kunit_vprintk(const struct kunit *test,
> > -			  const char *level,
> > -			  struct va_format *vaf)
> > -{
> > -	kunit_printk_emit(level[1] - '0', "\t# %s: %pV", test->name, vaf);
> > -}
> > -
> > -static void kunit_print_tap_version(void)
> > -{
> > -	static bool kunit_has_printed_tap_version;
> > -
> > -	if (!kunit_has_printed_tap_version) {
> > -		kunit_printk_emit(LOGLEVEL_INFO, "TAP version 14\n");
> > -		kunit_has_printed_tap_version = true;
> > -	}
> > -}
> > -
> >  static size_t kunit_test_cases_len(struct kunit_case *test_cases)
> >  {
> >  	struct kunit_case *test_case;
> > @@ -63,11 +29,9 @@ static size_t kunit_test_cases_len(struct kunit_case *test_cases)
> >  
> >  static void kunit_print_subtest_start(struct kunit_suite *suite)
> >  {
> > -	kunit_print_tap_version();
> > -	kunit_printk_emit(LOGLEVEL_INFO, "\t# Subtest: %s\n", suite->name);
> > -	kunit_printk_emit(LOGLEVEL_INFO,
> > -			  "\t1..%zd\n",
> > -			  kunit_test_cases_len(suite->test_cases));
> > +	pr_info_once("TAP version 14\n");
> > +	pr_info("\t# Subtest: %s\n", suite->name);
> > +	pr_info("\t1..%zd\n", kunit_test_cases_len(suite->test_cases));
> >  }
> >  
> >  static void kunit_print_ok_not_ok(bool should_indent,
> > @@ -87,9 +51,8 @@ static void kunit_print_ok_not_ok(bool should_indent,
> >  	else
> >  		ok_not_ok = "not ok";
> >  
> > -	kunit_printk_emit(LOGLEVEL_INFO,
> > -			  "%s%s %zd - %s\n",
> > -			  indent, ok_not_ok, test_number, description);
> > +	pr_info("%s%s %zd - %s\n",
> > +		indent, ok_not_ok, test_number, description);
> >  }
> >  
> >  static bool kunit_suite_has_succeeded(struct kunit_suite *suite)
> > @@ -133,11 +96,11 @@ static void kunit_print_string_stream(struct kunit *test,
> >  		kunit_err(test,
> >  			  "Could not allocate buffer, dumping stream:\n");
> >  		list_for_each_entry(fragment, &stream->fragments, node) {
> > -			kunit_err(test, fragment->fragment);
> > +			kunit_err(test, "%s", fragment->fragment);
> >  		}
> >  		kunit_err(test, "\n");
> >  	} else {
> > -		kunit_err(test, buf);
> > +		kunit_err(test, "%s", buf);
> >  		kunit_kfree(test, buf);
> >  	}
> >  }
> > @@ -505,19 +468,29 @@ void kunit_cleanup(struct kunit *test)
> >  	}
> >  }
> >  
> > -void kunit_printk(const char *level,
> > -		  const struct kunit *test,
> > -		  const char *fmt, ...)
> > +void kunit_printk(const struct kunit *test, const char *fmt, ...)
> >  {
> > +	char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1] = "\0";
> >  	struct va_format vaf;
> >  	va_list args;
> > +	int kern_level;
> >  
> >  	va_start(args, fmt);
> >  
> > +	while ((kern_level = printk_get_level(fmt)) != 0) {
> > +		size_t size = printk_skip_level(fmt) - fmt;
> > +
> > +		if (kern_level >= '0' && kern_level <= '7') {
> > +			memcpy(lvl, fmt,  size);
> > +			lvl[size] = '\0';
> > +		}
> > +		fmt += size;
> > +	}
> > +
> >  	vaf.fmt = fmt;
> >  	vaf.va = &args;
> >  
> > -	kunit_vprintk(test, level, &vaf);
> > +	printk("%s\t# %s %pV\n", lvl, test->name, &vaf);
> >  
> >  	va_end(args);
> >  }
> 
> How is this simpler?
> 
> If we are okay with dynamically adding the KERN_<LEVEL> and %pV (and I
> don't think that Sergey is),

Sergey may well be in the minority overall as %pV
is now very frequently
used throughout the kernel.

$ git grep "%pV" | wc -l
241

 then wouldn't it be easier to pass in the
> kernel level as a separate parameter and then strip off all printk
> headers like this:

Depends on whether or not you care for overall
object size.  Consolidated formats with the
embedded KERN_<LEVEL> like suggested are smaller
overall object size.

This style is also already used in the kernel.

> I don't know. I am clearly not an expert on this topic, but I don't see
> the merit of the while loop you added above or dropping the level param.

The while use is only to avoid misuses with consecutive 
KERN_<LEVEL> formats, which had happened in the past.

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