Patch "linux/dim: Do nothing if no time delta between samples" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    linux/dim: Do nothing if no time delta between samples

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     linux-dim-do-nothing-if-no-time-delta-between-sample.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4985ecdc4e83f4844ed996e3363ed92d766226af
Author: Roy Novich <royno@xxxxxxxxxx>
Date:   Sun May 7 16:57:43 2023 +0300

    linux/dim: Do nothing if no time delta between samples
    
    [ Upstream commit 162bd18eb55adf464a0fa2b4144b8d61c75ff7c2 ]
    
    Add return value for dim_calc_stats. This is an indication for the
    caller if curr_stats was assigned by the function. Avoid using
    curr_stats uninitialized over {rdma/net}_dim, when no time delta between
    samples. Coverity reported this potential use of an uninitialized
    variable.
    
    Fixes: 4c4dbb4a7363 ("net/mlx5e: Move dynamic interrupt coalescing code to include/linux")
    Fixes: cb3c7fd4f839 ("net/mlx5e: Support adaptive RX coalescing")
    Signed-off-by: Roy Novich <royno@xxxxxxxxxx>
    Reviewed-by: Aya Levin <ayal@xxxxxxxxxx>
    Reviewed-by: Saeed Mahameed <saeedm@xxxxxxxxxx>
    Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
    Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxx>
    Reviewed-by: Michal Kubiak <michal.kubiak@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20230507135743.138993-1-tariqt@xxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/dim.h b/include/linux/dim.h
index 6c5733981563e..f343bc9aa2ec9 100644
--- a/include/linux/dim.h
+++ b/include/linux/dim.h
@@ -236,8 +236,9 @@ void dim_park_tired(struct dim *dim);
  *
  * Calculate the delta between two samples (in data rates).
  * Takes into consideration counter wrap-around.
+ * Returned boolean indicates whether curr_stats are reliable.
  */
-void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
+bool dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
 		    struct dim_stats *curr_stats);
 
 /**
diff --git a/lib/dim/dim.c b/lib/dim/dim.c
index 38045d6d05381..e89aaf07bde50 100644
--- a/lib/dim/dim.c
+++ b/lib/dim/dim.c
@@ -54,7 +54,7 @@ void dim_park_tired(struct dim *dim)
 }
 EXPORT_SYMBOL(dim_park_tired);
 
-void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
+bool dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
 		    struct dim_stats *curr_stats)
 {
 	/* u32 holds up to 71 minutes, should be enough */
@@ -66,7 +66,7 @@ void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
 			     start->comp_ctr);
 
 	if (!delta_us)
-		return;
+		return false;
 
 	curr_stats->ppms = DIV_ROUND_UP(npkts * USEC_PER_MSEC, delta_us);
 	curr_stats->bpms = DIV_ROUND_UP(nbytes * USEC_PER_MSEC, delta_us);
@@ -79,5 +79,6 @@ void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
 	else
 		curr_stats->cpe_ratio = 0;
 
+	return true;
 }
 EXPORT_SYMBOL(dim_calc_stats);
diff --git a/lib/dim/net_dim.c b/lib/dim/net_dim.c
index 53f6b9c6e9366..4e32f7aaac86c 100644
--- a/lib/dim/net_dim.c
+++ b/lib/dim/net_dim.c
@@ -227,7 +227,8 @@ void net_dim(struct dim *dim, struct dim_sample end_sample)
 				  dim->start_sample.event_ctr);
 		if (nevents < DIM_NEVENTS)
 			break;
-		dim_calc_stats(&dim->start_sample, &end_sample, &curr_stats);
+		if (!dim_calc_stats(&dim->start_sample, &end_sample, &curr_stats))
+			break;
 		if (net_dim_decision(&curr_stats, dim)) {
 			dim->state = DIM_APPLY_NEW_PROFILE;
 			schedule_work(&dim->work);
diff --git a/lib/dim/rdma_dim.c b/lib/dim/rdma_dim.c
index 15462d54758d3..88f7794867078 100644
--- a/lib/dim/rdma_dim.c
+++ b/lib/dim/rdma_dim.c
@@ -88,7 +88,8 @@ void rdma_dim(struct dim *dim, u64 completions)
 		nevents = curr_sample->event_ctr - dim->start_sample.event_ctr;
 		if (nevents < DIM_NEVENTS)
 			break;
-		dim_calc_stats(&dim->start_sample, curr_sample, &curr_stats);
+		if (!dim_calc_stats(&dim->start_sample, curr_sample, &curr_stats))
+			break;
 		if (rdma_dim_decision(&curr_stats, dim)) {
 			dim->state = DIM_APPLY_NEW_PROFILE;
 			schedule_work(&dim->work);