On 04/03/15 10:12, Russell King wrote:
Signed-off-by: Russell King rmk+kernel@arm.linux.org.uk
Some commit text would be nice for us 5 years from now when we wonder why this patch was applied.
I suspect the commit text would go like this:
clk_add_alias() calls clk_get() followed by clk_put() but in between those two calls it saves away the struct clk pointer to a clk_lookup structure. This leaves the 'clk' member of the clk_lookup pointing at freed memory on configurations where CONFIG_COMMON_CLK=y. This is a problem because clk_get_sys() will eventually try to dereference the freed pointer by calling __clk_get_hw() on it. Fix this by saving away the struct clk_hw pointer instead of the struct clk pointer so that when we try to create a per-user struct clk in clk_get_sys() we don't dereference a junk pointer.
Now the question is does any of this matter for the 4.0 release. From what I can tell, the answer is no.
$ git grep 'clk_add_alias' v4.0-rc6 v4.0-rc6:arch/arm/mach-davinci/da850.c: clk_add_alias("async", da850_cpufreq_device.name, v4.0-rc6:arch/arm/mach-omap1/board-nokia770.c: clk_add_alias("hwa_sys_ck", NULL, "bclk", NULL); v4.0-rc6:arch/arm/mach-pxa/eseries.c: clk_add_alias("CLK_CK48M", e740_t7l66xb_device.name, v4.0-rc6:arch/arm/mach-pxa/eseries.c: clk_add_alias("CLK_CK3P6MI", e750_tc6393xb_device.name, v4.0-rc6:arch/arm/mach-pxa/eseries.c: clk_add_alias("CLK_CK3P6MI", e800_tc6393xb_device.name, v4.0-rc6:arch/arm/mach-pxa/lubbock.c: clk_add_alias("SA1111_CLK", NULL, "GPIO11_CLK", NULL); v4.0-rc6:arch/arm/mach-pxa/tosa.c: clk_add_alias("CLK_CK3P6MI", tc6393xb_device.name, "GPIO11_CLK", NULL); v4.0-rc6:arch/mips/alchemy/common/clock.c: clk_add_alias(t->alias, NULL, t->base, NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ahb", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ref", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ref", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ref", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("wdt", NULL, "ref", NULL); v4.0-rc6:arch/mips/ath79/clock.c: clk_add_alias("uart", NULL, "ref", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-tmu-sh3.0", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-tmu.0", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-tmu.1", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-tmu.2", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-mtu2", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-cmt-16.0", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("fck", "sh-cmt-32.0", "peripheral_clk", NULL); v4.0-rc6:arch/sh/kernel/cpu/clock-cpg.c: clk_add_alias("sci_ick", NULL, "peripheral_clk", NULL);
All of these architectures and platforms have CONFIG_COMMON_CLK=n, so there doesn't seem to be any regression that these patches are fixing. That isn't to say the patches are bad, just that they aren't urgent for the upcoming release.