Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Christophe JAILLET]

Le 09/05/2017 à 17:18, Joe Perches a écrit :
> On Mon, 2017-05-08 at 17:35 -0700, Florian Fainelli wrote:
> > On 05/08/2017 04:46 PM, Julia Lawall wrote:
> > > On Mon, 8 May 2017, Joe Perches wrote:
> > > > Each time -EPROBE_DEFER occurs, another set of calls to
> > > > dsa_switch_alloc and dev_kzalloc also occurs.
> > > >
> > > > Perhaps it'd be better to do:
> > > >
> > > > 	if (ps->netdev) {
> > > > 		devm_kfree(&devmdev->dev, ps);
> > > > 		devm_kfree(&mdiodev->dev, ds);
> > > > 		return -EPROBE_DEFER;
> > > > 	}
> > > Is EPROBE_DEFER handled differently than other kinds of errors?
> > In the core device driver model, yes, EPROBE_DEFER is treated
> > differently than other errors because it puts the driver on a retry queue.
> >
> > EPROBE_DEFER is already a slow and exceptional path, and this is a
> > mock-up driver, so I am not sure what value there is in trying to
> > balance devm_kzalloc() with corresponding devm_kfree()...
> Example code should be as correct as possible.
Le 09/05/2017 à 17:18, Joe Perches a écrit :
> On Mon, 2017-05-08 at 17:35 -0700, Florian Fainelli wrote:
> > On 05/08/2017 04:46 PM, Julia Lawall wrote:
> > > On Mon, 8 May 2017, Joe Perches wrote:
> > > > Each time -EPROBE_DEFER occurs, another set of calls to
> > > > dsa_switch_alloc and dev_kzalloc also occurs.
> > > >
> > > > Perhaps it'd be better to do:
> > > >
> > > > 	if (ps->netdev) {
> > > > 		devm_kfree(&devmdev->dev, ps);
> > > > 		devm_kfree(&mdiodev->dev, ds);
> > > > 		return -EPROBE_DEFER;
> > > > 	}
> > > Is EPROBE_DEFER handled differently than other kinds of errors?
> > In the core device driver model, yes, EPROBE_DEFER is treated
> > differently than other errors because it puts the driver on a retry queue.
> >
> > EPROBE_DEFER is already a slow and exceptional path, and this is a
> > mock-up driver, so I am not sure what value there is in trying to
> > balance devm_kzalloc() with corresponding devm_kfree()...
> Example code should be as correct as possible.
(* number of people/mailing list in copy has been reduced *)


The coccinelle script below gives the following list of candidates for 
such improvement.

char/hw_random/omap-rng.c
clk/clk-si5351.c
clk/clk-versaclock5.c
crypto/mediatek/mtk-platform.c
devfreq/rk3399_dmc.c
dma/mv_xor_v2.c
dma/omap-dma.c
gpu/drm/arc/arcpgu_hdmi.c
gpu/drm/bridge/dumb-vga-dac.c
gpu/drm/bridge/lvds-encoder.c
gpu/drm/exynos/exynos_dp.c
gpu/drm/exynos/exynos_drm_dsi.c
gpu/drm/imx/dw_hdmi-imx.c
gpu/drm/mediatek/mtk_dpi.c
gpu/drm/mediatek/mtk_drm_ddp_comp.c
gpu/drm/mediatek/mtk_dsi.c
gpu/drm/panel/panel-lvds.c
gpu/drm/panel/panel-simple.c
gpu/drm/panel/panel-sitronix-st7789v.c
gpu/drm/rcar-du/rcar_du_lvdscon.c
gpu/drm/rockchip/cdn-dp-core.c
gpu/drm/rockchip/dw_hdmi-rockchip.c
gpu/drm/sti/sti_hdmi.c
gpu/drm/tegra/sor.c
gpu/drm/tilcdc/tilcdc_panel.c
gpu/drm/vc4/vc4_hdmi.c
gpu/ipu-v3/ipu-common.c
gpu/ipu-v3/ipu-pre.c
gpu/ipu-v3/ipu-prg.c
hwtracing/coresight/coresight-stm.c
i2c/busses/i2c-designware-platdrv.c
i2c/busses/i2c-mv64xxx.c
i2c/muxes/i2c-mux-gpio.c
i2c/muxes/i2c-mux-pinctrl.c
i2c/muxes/i2c-mux-reg.c
iommu/mtk_iommu.c
iommu/mtk_iommu_v1.c
irqchip/qcom-irq-combiner.c
mailbox/mailbox-test.c
media/i2c/mt9m111.c
media/i2c/ov2640.c
media/i2c/ov7670.c
media/i2c/smiapp/smiapp-core.c
media/i2c/soc_camera/imx074.c
media/platform/coda/coda-common.c
media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c
media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c
media/platform/s5p-cec/s5p_cec.c
media/platform/sti/cec/stih-cec.c
memory/tegra/tegra124-emc.c
mfd/twl6040.c
mtd/nand/lpc32xx_mlc.c
mtd/nand/lpc32xx_slc.c
net/dsa/dsa_loop.c
net/ethernet/mediatek/mtk_eth_soc.c
net/phy/xilinx_gmii2rgmii.c
net/wireless/ti/wlcore/spi.c
pci/host/pcie-iproc-platform.c
phy/phy-exynos5250-sata.c
phy/phy-mt65xx-usb3.c
phy/phy-qcom-qusb2.c
phy/phy-sun4i-usb.c
pinctrl/core.c
pinctrl/pinctrl-at91.c
platform/x86/intel_cht_int33fe.c
power/supply/act8945a_charger.c
power/supply/axp20x_ac_power.c
power/supply/axp20x_battery.c
power/supply/axp288_charger.c
power/supply/bq24190_charger.c
power/supply/cpcap-charger.c
power/supply/gpio-charger.c
soc/bcm/raspberrypi-power.c
thermal/samsung/exynos_tmu.c
tty/serial/8250/8250_dw.c
tty/serial/max310x.c
tty/serial/sccnxp.c
usb/chipidea/ci_hdrc_msm.c
usb/gadget/udc/mv_udc_core.c
usb/host/xhci-mtk.c
usb/mtu3/mtu3_plat.c
usb/musb/sunxi.c
usb/phy/phy-am335x.c
usb/phy/phy-generic.c
usb/phy/phy-twl6030-usb.c
video/backlight/hx8357.c
video/backlight/lp855x_bl.c
video/fbdev/simplefb.c


Coccinelle script :
=================
// find calls to kmalloc or equivalent function
@call@
expression ptr;
position p;
@@

(
*   ptr@p = kmalloc(...)
|
*   ptr@p = kzalloc(...)
|
*   ptr@p = kcalloc(...)
|
*   ptr@p = kmalloc_array(...)
|
*   ptr@p = devm_kmalloc(...)
|
*   ptr@p = devm_kzalloc(...)
|
*   ptr@p = devm_kcalloc(...)
|
*   ptr@p = devm_kmalloc_array(...)
)
 ...
*  return -EPROBE_DEFER;