Re: [PATCH resent] perf/x86/amd/uncore: Fix exception handling in amd_uncore_cpu_up_prepare()

Re: [PATCH resent] perf/x86/amd/uncore: Fix exception handling in amd_uncore_cpu_up_prepare()

[Adrian Hunter]

On 25/03/23 16:15, Markus Elfring wrote:
> Date: Fri, 17 Mar 2023 13:13:14 +0100
> 
> The label “fail” was used to jump to another pointer check despite of
> the detail in the implementation of the function “amd_uncore_cpu_up_prepare”
> that it was determined already that the corresponding variable contained
> a null pointer (because of a failed function call in two cases).
> 
> 1. Thus return directly after a call of the function “amd_uncore_alloc”
>    failed in the first if branch.
> 
> 2. Use more appropriate labels instead.
> 
> 3. Reorder jump targets at the end.
> 
> 4. Delete a redundant check and kfree() call.
> 
> 5. Omit an explicit initialisation for the local variable “uncore_llc”.
> 
> 
> This issue was detected by using the Coccinelle software.
> 
> Fixes: 39621c5808f5dda75d03dc4b2d4d2b13a5a1c34b ("perf/x86/amd/uncore: Use dynamic events array")
> Fixes: 503d3291a937b726757c1f7c45fa02389d2f4324 ("perf/x86/amd: Try to fix some mem allocation failure handling")

Commit should be only the first 12 characters of the hash.
Refer:	https://docs.kernel.org/process/submitting-patches.html

But this is not a fix. Redundant calls to kfree do not break
anything.

Also avoid using the term "exception" since, in x86, exceptions are
hardware events.  Better to just call it "error handling".

> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  arch/x86/events/amd/uncore.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
> index 83f15fe411b3..0a9b5cb97bb4 100644
> --- a/arch/x86/events/amd/uncore.c
> +++ b/arch/x86/events/amd/uncore.c
> @@ -440,13 +440,13 @@ amd_uncore_events_alloc(unsigned int num, unsigned int cpu)
> 
>  static int amd_uncore_cpu_up_prepare(unsigned int cpu)
>  {
> -	struct amd_uncore *uncore_nb = NULL, *uncore_llc = NULL;
> +	struct amd_uncore *uncore_nb = NULL, *uncore_llc;
> 
>  	if (amd_uncore_nb) {
>  		*per_cpu_ptr(amd_uncore_nb, cpu) = NULL;
>  		uncore_nb = amd_uncore_alloc(cpu);
>  		if (!uncore_nb)
> -			goto fail;
> +			return -ENOMEM;
>  		uncore_nb->cpu = cpu;
>  		uncore_nb->num_counters = num_counters_nb;
>  		uncore_nb->rdpmc_base = RDPMC_BASE_NB;
> @@ -455,7 +455,7 @@ static int amd_uncore_cpu_up_prepare(unsigned int cpu)
>  		uncore_nb->pmu = &amd_nb_pmu;
>  		uncore_nb->events = amd_uncore_events_alloc(num_counters_nb, cpu);
>  		if (!uncore_nb->events)
> -			goto fail;
> +			goto free_nb;
>  		uncore_nb->id = -1;
>  		*per_cpu_ptr(amd_uncore_nb, cpu) = uncore_nb;
>  	}
> @@ -464,7 +464,7 @@ static int amd_uncore_cpu_up_prepare(unsigned int cpu)
>  		*per_cpu_ptr(amd_uncore_llc, cpu) = NULL;
>  		uncore_llc = amd_uncore_alloc(cpu);
>  		if (!uncore_llc)
> -			goto fail;
> +			goto check_uncore_nb;
>  		uncore_llc->cpu = cpu;
>  		uncore_llc->num_counters = num_counters_llc;
>  		uncore_llc->rdpmc_base = RDPMC_BASE_LLC;
> @@ -473,24 +473,22 @@ static int amd_uncore_cpu_up_prepare(unsigned int cpu)
>  		uncore_llc->pmu = &amd_llc_pmu;
>  		uncore_llc->events = amd_uncore_events_alloc(num_counters_llc, cpu);
>  		if (!uncore_llc->events)
> -			goto fail;
> +			goto free_llc;
>  		uncore_llc->id = -1;
>  		*per_cpu_ptr(amd_uncore_llc, cpu) = uncore_llc;
>  	}
> 
>  	return 0;
> 
> -fail:
> +free_llc:
> +	kfree(uncore_llc);
> +check_uncore_nb:
>  	if (uncore_nb) {
>  		kfree(uncore_nb->events);
> +free_nb:
>  		kfree(uncore_nb);
>  	}
> 
> -	if (uncore_llc) {
> -		kfree(uncore_llc->events);
> -		kfree(uncore_llc);
> -	}
> -
>  	return -ENOMEM;
>  }
> 
> --
> 2.40.0
> 

Re: [PATCH resent] perf/x86/amd/uncore: Fix exception handling in amd_uncore_cpu_up_prepare()

[Peter Zijlstra]

On Mon, Mar 27, 2023 at 12:11:54PM +0300, Adrian Hunter wrote:
> On 25/03/23 16:15, Markus Elfring wrote:
> > Date: Fri, 17 Mar 2023 13:13:14 +0100
> > 
> > The label “fail” was used to jump to another pointer check despite of
> > the detail in the implementation of the function “amd_uncore_cpu_up_prepare”
> > that it was determined already that the corresponding variable contained
> > a null pointer (because of a failed function call in two cases).
> > 
> > 1. Thus return directly after a call of the function “amd_uncore_alloc”
> >    failed in the first if branch.
> > 
> > 2. Use more appropriate labels instead.
> > 
> > 3. Reorder jump targets at the end.
> > 
> > 4. Delete a redundant check and kfree() call.
> > 
> > 5. Omit an explicit initialisation for the local variable “uncore_llc”.
> > 
> > 
> > This issue was detected by using the Coccinelle software.
> > 
> > Fixes: 39621c5808f5dda75d03dc4b2d4d2b13a5a1c34b ("perf/x86/amd/uncore: Use dynamic events array")
> > Fixes: 503d3291a937b726757c1f7c45fa02389d2f4324 ("perf/x86/amd: Try to fix some mem allocation failure handling")
> 
> Commit should be only the first 12 characters of the hash.
> Refer:	https://docs.kernel.org/process/submitting-patches.html
> 
> But this is not a fix. Redundant calls to kfree do not break
> anything.
> 
> Also avoid using the term "exception" since, in x86, exceptions are
> hardware events.  Better to just call it "error handling".

Don't feed the trolls; Markus is a bot or other weird construct that's
been banned from lkml.

[PATCH RESEND] perf cputopo: Improve exception handling in build_cpu_topology()

[Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Thu, 23 Mar 2023 22:00:07 +0100

The label “done” was used to jump to another pointer check despite of
the detail in the implementation of the function “build_cpu_topology”
that it was determined already that a corresponding variable contained
a null pointer because of a failed call of the function “fopen”.

1. Thus use more appropriate labels instead.

2. Reorder jump targets at the end.

3. Delete a redundant check.


This issue was detected by using the Coccinelle software.

Fixes: 5135d5efcbb4 ("perf tools: Add cpu_topology object")
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 tools/perf/util/cputopo.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
index e08797c3cdbc..fd185951ee2c 100644
--- a/tools/perf/util/cputopo.c
+++ b/tools/perf/util/cputopo.c
@@ -112,10 +112,10 @@ static int build_cpu_topology(struct cpu_topology *tp, int cpu)
 	}
 	fp = fopen(filename, "r");
 	if (!fp)
-		goto done;
+		goto exit;

 	if (getline(&buf, &len, fp) <= 0)
-		goto done;
+		goto close_file;

 	p = strchr(buf, '\n');
 	if (p)
@@ -131,10 +131,10 @@ static int build_cpu_topology(struct cpu_topology *tp, int cpu)
 		buf = NULL;
 	}
 	ret = 0;
-done:
-	if (fp)
-		fclose(fp);
 	free(buf);
+close_file:
+	fclose(fp);
+exit:
 	return ret;
 }

--
2.40.0