[PATCH RESEND] perf/x86/amd/uncore: turn amd_uncore_ctx events into a flexible array

[PATCH RESEND] perf/x86/amd/uncore: turn amd_uncore_ctx events into a flexible array

[Rosen Penev]

The events pointer was kzalloc_node()'d immediately after the parent
struct allocation, with the count (pmu->num_counters) trivially
available beforehand.  Move events to the struct tail as a flexible
array member and fold the two allocations into a single kzalloc_node()
with struct_size(), dropping the separate kfree(ctx->events) in the
free path.

Assisted-by: Claude:Opus-4.7
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 arch/x86/events/amd/uncore.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index 7181973b5b12..74b9c92d517a 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -39,11 +39,11 @@ static int pmu_version;
 struct amd_uncore_ctx {
 	int refcnt;
 	int cpu;
-	struct perf_event **events;
 	unsigned long active_mask[BITS_TO_LONGS(NUM_COUNTERS_MAX)];
 	int nr_active;
 	struct hrtimer hrtimer;
 	u64 hrtimer_duration;
+	struct perf_event *events[];
 };
 
 struct amd_uncore_pmu {
@@ -519,10 +519,8 @@ static void amd_uncore_ctx_free(struct amd_uncore *uncore, unsigned int cpu)
 		if (cpu == ctx->cpu)
 			cpumask_clear_cpu(cpu, &pmu->active_mask);
 
-		if (!--ctx->refcnt) {
-			kfree(ctx->events);
+		if (!--ctx->refcnt)
 			kfree(ctx);
-		}
 
 		*per_cpu_ptr(pmu->ctx, cpu) = NULL;
 	}
@@ -567,18 +565,11 @@ static int amd_uncore_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
 		/* Allocate context if sibling does not exist */
 		if (!curr) {
 			node = cpu_to_node(cpu);
-			curr = kzalloc_node(sizeof(*curr), GFP_KERNEL, node);
+			curr = kzalloc_node(struct_size(curr, events, pmu->num_counters), GFP_KERNEL, node);
 			if (!curr)
 				goto fail;
 
 			curr->cpu = cpu;
-			curr->events = kzalloc_node(sizeof(*curr->events) *
-						    pmu->num_counters,
-						    GFP_KERNEL, node);
-			if (!curr->events) {
-				kfree(curr);
-				goto fail;
-			}
 
 			amd_uncore_init_hrtimer(curr);
 			curr->hrtimer_duration = (u64)update_interval * NSEC_PER_MSEC;
-- 
2.55.0

Re: [PATCH RESEND] perf/x86/amd/uncore: turn amd_uncore_ctx events into a flexible array

[Sandipan Das]

On 16-09-2026 06:15, Rosen Penev wrote:
> The events pointer was kzalloc_node()'d immediately after the parent
> struct allocation, with the count (pmu->num_counters) trivially
> available beforehand.  Move events to the struct tail as a flexible
> array member and fold the two allocations into a single kzalloc_node()
> with struct_size(), dropping the separate kfree(ctx->events) in the
> free path.
> 
> Assisted-by: Claude:Opus-4.7
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  arch/x86/events/amd/uncore.c | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
> index 7181973b5b12..74b9c92d517a 100644
> --- a/arch/x86/events/amd/uncore.c
> +++ b/arch/x86/events/amd/uncore.c
> @@ -39,11 +39,11 @@ static int pmu_version;
>  struct amd_uncore_ctx {
>  	int refcnt;
>  	int cpu;
> -	struct perf_event **events;
>  	unsigned long active_mask[BITS_TO_LONGS(NUM_COUNTERS_MAX)];
>  	int nr_active;
>  	struct hrtimer hrtimer;
>  	u64 hrtimer_duration;
> +	struct perf_event *events[];
>  };
>  
>  struct amd_uncore_pmu {
> @@ -519,10 +519,8 @@ static void amd_uncore_ctx_free(struct amd_uncore *uncore, unsigned int cpu)
>  		if (cpu == ctx->cpu)
>  			cpumask_clear_cpu(cpu, &pmu->active_mask);
>  
> -		if (!--ctx->refcnt) {
> -			kfree(ctx->events);
> +		if (!--ctx->refcnt)
>  			kfree(ctx);
> -		}
>  
>  		*per_cpu_ptr(pmu->ctx, cpu) = NULL;
>  	}
> @@ -567,18 +565,11 @@ static int amd_uncore_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
>  		/* Allocate context if sibling does not exist */
>  		if (!curr) {
>  			node = cpu_to_node(cpu);
> -			curr = kzalloc_node(sizeof(*curr), GFP_KERNEL, node);
> +			curr = kzalloc_node(struct_size(curr, events, pmu->num_counters), GFP_KERNEL, node);
>  			if (!curr)
>  				goto fail;
>  
>  			curr->cpu = cpu;
> -			curr->events = kzalloc_node(sizeof(*curr->events) *
> -						    pmu->num_counters,
> -						    GFP_KERNEL, node);
> -			if (!curr->events) {
> -				kfree(curr);
> -				goto fail;
> -			}
>  
>  			amd_uncore_init_hrtimer(curr);
>  			curr->hrtimer_duration = (u64)update_interval * NSEC_PER_MSEC;

Reviewed-by: Sandipan Das <sandipan.das@amd.com>