Messages in this thread | | | Subject | Re: [PATCH v5 04/21] x86/resctrl: Group struct rdt_hw_domain cleanup | From | James Morse <> | Date | Wed, 29 Jun 2022 12:07:20 +0100 |
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Hi Shaopeng,
On 29/06/2022 09:33, tan.shaopeng@fujitsu.com wrote: >> domain_add_cpu() and domain_remove_cpu() need to kfree() the child arrays >> that were allocated by domain_setup_ctrlval(). >> >> As this memory is moved around, and new arrays are created, adjusting the >> error handling cleanup code becomes noisier. >> >> To simplify this, move all the kfree() calls into a domain_free() helper. >> This depends on struct rdt_hw_domain being kzalloc()d, allowing it to >> unconditionally kfree() all the child arrays.
>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c >> b/arch/x86/kernel/cpu/resctrl/core.c >> index 25f30148478b..e37889f7a1a5 100644 >> --- a/arch/x86/kernel/cpu/resctrl/core.c >> +++ b/arch/x86/kernel/cpu/resctrl/core.c >> @@ -414,6 +414,13 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 >> *dc, u32 *dm) >> } >> } >> >> +static void domain_free(struct rdt_hw_domain *hw_dom) { >> + kfree(hw_dom->ctrl_val); >> + kfree(hw_dom->mbps_val); >> + kfree(hw_dom); >> +} >> + >> static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d) { >> struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r); @@ -488,7 >> +495,7 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r) >> rdt_domain_reconfigure_cdp(r); >> >> if (r->alloc_capable && domain_setup_ctrlval(r, d)) { >> - kfree(hw_dom); >> + domain_free(hw_dom);
> domain_free(hw_dom) is executed when fails allocated hw_dom->ctrl_val > by kmalloc_array() in domain_setup_ctrlval(r, d), > but hw_dom->ctrl_val is freed in domain_free(hw_dom). > > Also, hw_dom->mbps_val is not allocated at this time, > but it is freed in domain_free(hw_dom).
Yes, this is deliberate. These cases end up doing: | kfree(NULL); which is harmless. kfree() checks for a NULL argument and does nothing.
The alternative would be to spread the cleanup all over the place, so it only calls kfree() on something that has been allocated - this would be more complex and easier to miss something.
> In addition,I tested this patch series on Intel(R) Xeon(R) Gold 6254 CPU with resctrl selftest. > It is no problem.
Thanks!
James
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