Re: [PATCH v3] kunit: fix failure to build without printk

[Joe Perches <joe@perches.com>]

On Tue, 2019-09-03 at 16:21 -0700, 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.
> 
> This fixes a build error[1] reported by Randy.
> 
> For context this change comes after much discussion. My first stab[2] at
> this was just to make the KUnit logging code compile out; however, it
> was agreed that if we were going to use vprintk_emit, then vprintk_emit
> should provide a no-op stub, which lead to my second attempt[3]. In
> response to me trying to stub out vprintk_emit, Sergey Senozhatsky
> suggested a way for me to remove our usage of vprintk_emit, which led to
> my third attempt at solving this[4].
> 
> In my previous version of this patch[4], I completely removed
> vprintk_emit, as suggested by Sergey; however, there was a bit of debate
> over whether Sergey's solution was the best. The debate arose due to
> Sergey's version resulting in a checkpatch warning, which resulted in a
> debate over correct printk usage. Joe Perches offered an alternative fix
> which was somewhat less far reaching than what Sergey had suggested and
> importantly relied on continuing to use %pV. Much of the debated
> centered around whether %pV should be widely used, and whether Sergey's
> version would result in object size bloat. Ultimately, we decided to go
> with Sergey's version.
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Link[1]: https://lore.kernel.org/linux-kselftest/c7229254-0d90-d90e-f3df-5b6d6fc0b51f@infradead.org/
> Link[2]: https://lore.kernel.org/linux-kselftest/20190827174932.44177-1-brendanhiggins@google.com/
> Link[3]: https://lore.kernel.org/linux-kselftest/20190827234835.234473-1-brendanhiggins@google.com/
> Link[4]: https://lore.kernel.org/linux-kselftest/20190828093143.163302-1-brendanhiggins@google.com/
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Tim.Bird@sony.com
> Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
> Reviewed-by: Petr Mladek <pmladek@suse.com>
> ---
> 
> Sorry for the long commit message, but given the long discussion (and
> some of the confusion that occurred in the discussion), it seemed
> appropriate to summarize the discussion around this patch up to this
> point (especially since one of the proposed patches was under a separate
> patch subject).
> 
> No changes have been made to this patch since v2, other than the commit
> log.
[]
> diff --git 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, ...);
> +#define kunit_print_level(KERN_LEVEL, test, fmt, ...) \
> +	printk(KERN_LEVEL "\t# %s: " fmt, (test)->name, ##__VA_ARGS__)

Non trivial notes:

Please do not use KERN_LEVEL as a macro argument.
It would just be a source of possible confusion.

Please use level or lvl like nearly every other macro
that does this uses.

And there is nothing wrong with using kunit_printk and it's
not necessary to use an odd name like kunit_printk_level.

$ git grep -P 'define\s+\w+_printk\(.*\b(level|lvl)'
drivers/block/drbd/drbd_int.h:#define drbd_printk(level, obj, fmt, args...) \
drivers/edac/amd76x_edac.c:#define amd76x_printk(level, fmt, arg...) \
drivers/edac/amd76x_edac.c:#define amd76x_mc_printk(mci, level, fmt, arg...) \
drivers/edac/cpc925_edac.c:#define cpc925_printk(level, fmt, arg...) \
drivers/edac/cpc925_edac.c:#define cpc925_mc_printk(mci, level, fmt, arg...) \
drivers/edac/e752x_edac.c:#define e752x_printk(level, fmt, arg...) \
drivers/edac/e752x_edac.c:#define e752x_mc_printk(mci, level, fmt, arg...) \
drivers/edac/e7xxx_edac.c:#define e7xxx_printk(level, fmt, arg...) \
drivers/edac/e7xxx_edac.c:#define e7xxx_mc_printk(mci, level, fmt, arg...) \
drivers/edac/edac_mc.h:#define edac_printk(level, prefix, fmt, arg...) \
drivers/edac/edac_mc.h:#define edac_mc_printk(mci, level, fmt, arg...) \
drivers/edac/edac_mc.h:#define edac_mc_chipset_printk(mci, level, prefix, fmt, arg...) \
drivers/edac/edac_mc.h:#define edac_device_printk(ctl, level, fmt, arg...) \
drivers/edac/edac_mc.h:#define edac_pci_printk(ctl, level, fmt, arg...) \
drivers/edac/fsl_ddr_edac.h:#define fsl_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i10nm_base.c:#define i10nm_printk(level, fmt, arg...)      \
drivers/edac/i5000_edac.c:#define i5000_printk(level, fmt, arg...) \
drivers/edac/i5000_edac.c:#define i5000_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i5400_edac.c:#define i5400_printk(level, fmt, arg...) \
drivers/edac/i5400_edac.c:#define i5400_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i7300_edac.c:#define i7300_printk(level, fmt, arg...) \
drivers/edac/i7300_edac.c:#define i7300_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i7core_edac.c:#define i7core_printk(level, fmt, arg...)                    \
drivers/edac/i7core_edac.c:#define i7core_mc_printk(mci, level, fmt, arg...)            \
drivers/edac/i82860_edac.c:#define i82860_printk(level, fmt, arg...) \
drivers/edac/i82860_edac.c:#define i82860_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i82875p_edac.c:#define i82875p_printk(level, fmt, arg...) \
drivers/edac/i82875p_edac.c:#define i82875p_mc_printk(mci, level, fmt, arg...) \
drivers/edac/i82975x_edac.c:#define i82975x_printk(level, fmt, arg...) \
drivers/edac/i82975x_edac.c:#define i82975x_mc_printk(mci, level, fmt, arg...) \
drivers/edac/ie31200_edac.c:#define ie31200_printk(level, fmt, arg...) \
drivers/edac/mpc85xx_edac.h:#define mpc85xx_printk(level, fmt, arg...) \
drivers/edac/mv64x60_edac.h:#define mv64x60_printk(level, fmt, arg...) \
drivers/edac/mv64x60_edac.h:#define mv64x60_mc_printk(mci, level, fmt, arg...) \
drivers/edac/pnd2_edac.c:#define pnd2_printk(level, fmt, arg...)                        \
drivers/edac/pnd2_edac.c:#define pnd2_mc_printk(mci, level, fmt, arg...)        \
drivers/edac/ppc4xx_edac.c:#define ppc4xx_edac_printk(level, fmt, arg...) \
drivers/edac/ppc4xx_edac.c:#define ppc4xx_edac_mc_printk(level, mci, fmt, arg...) \
drivers/edac/r82600_edac.c:#define r82600_printk(level, fmt, arg...) \
drivers/edac/r82600_edac.c:#define r82600_mc_printk(mci, level, fmt, arg...) \
drivers/edac/sb_edac.c:#define sbridge_printk(level, fmt, arg...)                       \
drivers/edac/sb_edac.c:#define sbridge_mc_printk(mci, level, fmt, arg...)               \
drivers/edac/skx_base.c:#define skx_printk(level, fmt, arg...)                  \
drivers/edac/skx_base.c:#define skx_mc_printk(mci, level, fmt, arg...)          \
drivers/edac/skx_common.h:#define skx_printk(level, fmt, arg...)                        \
drivers/edac/skx_common.h:#define skx_mc_printk(mci, level, fmt, arg...)                \
drivers/infiniband/hw/usnic/usnic_log.h:#define usnic_printk(lvl, args...) \
drivers/infiniband/ulp/ipoib/ipoib.h:#define ipoib_printk(level, priv, format, arg...)  \
drivers/input/mouse/psmouse.h:#define psmouse_printk(level, psmouse, format, ...)       \
drivers/media/tuners/mc44s803.c:#define mc_printk(level, format, arg...)        \
drivers/media/tuners/tda18271-priv.h:#define tda_printk(st, lvl, fmt, arg...)                   \
drivers/media/usb/uvc/uvcvideo.h:#define uvc_printk(level, msg...) \
drivers/net/ethernet/freescale/ucc_geth.c:#define ugeth_printk(level, format, arg...)  \
drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cpp.h:#define nfp_printk(level, cpp, fmt, args...) \
drivers/net/phy/phylink.c:#define phylink_printk(level, pl, fmt, ...) \
drivers/scsi/ipr.h:#define ipr_res_printk(level, ioa_cfg, bus, target, lun, fmt, ...) \
drivers/scsi/ipr.h:#define ipr_ra_printk(level, ioa_cfg, ra, fmt, ...) \
drivers/scsi/qla4xxx/ql4_def.h:#define ql4_printk(level, ha, format, arg...) \
drivers/scsi/sym53c8xx_2/sym_hipd.c:#define sym_printk(lvl, tp, cp, fmt, v...) do { \
drivers/usb/atm/usbatm.h:#define atm_printk(level, instance, format, arg...)    \
include/linux/hid.h:#define hid_printk(level, hid, fmt, arg...)         \
include/linux/netdevice.h:#define netif_printk(priv, type, level, dev, fmt, args...)    \
include/linux/pci.h:#define pci_printk(level, pdev, fmt, arg...) \
include/media/v4l2-common.h:#define v4l_printk(level, name, adapter, addr, fmt, arg...) \
include/media/v4l2-common.h:#define v4l_client_printk(level, client, fmt, arg...)                           \
include/media/v4l2-common.h:#define v4l2_printk(level, dev, fmt, arg...) \
include/net/cfg80211.h:#define wiphy_printk(level, wiphy, format, args...)              \
include/sound/core.h:#define __snd_printk(level, file, line, format, ...) \
net/bridge/br_private.h:#define br_printk(level, br, format, args...)   \