Re: [PATCH] interconnect:Replace mutex with rt_mutex for icc_bw_lock

From: Georgi Djakov
Date: Tue Feb 20 2024 - 06:35:19 EST


Hello,

On 20.02.24 9:43, Rumeng Wang wrote:
From: wangrumeng <wangrumeng@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

Replace existing mutex with rt_mutex to prevent priority inversion
between clients, which can cause unacceptable delays in some cases.

Signed-off-by: wangrumeng <wangrumeng@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

A similar patch [1] has been posted some time ago. Please check the review
comments.

Thanks,
Georgi

[1] https://lore.kernel.org/all/20220906191423.30109-1-quic_mdtipton@xxxxxxxxxxx/

---
drivers/interconnect/core.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
index 50bac2d79d9b..467d42cc7e49 100644
--- a/drivers/interconnect/core.c
+++ b/drivers/interconnect/core.c
@@ -14,6 +14,7 @@
#include <linux/interconnect-provider.h>
#include <linux/list.h>
#include <linux/mutex.h>
+#include <linux/rtmutex.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/overflow.h>
@@ -28,7 +29,7 @@ static LIST_HEAD(icc_providers);
static int providers_count;
static bool synced_state;
static DEFINE_MUTEX(icc_lock);
-static DEFINE_MUTEX(icc_bw_lock);
+static DEFINE_RT_MUTEX(icc_bw_lock);
static struct dentry *icc_debugfs_dir;
static void icc_summary_show_one(struct seq_file *s, struct icc_node *n)
@@ -698,7 +699,7 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
if (WARN_ON(IS_ERR(path) || !path->num_nodes))
return -EINVAL;
- mutex_lock(&icc_bw_lock);
+ rt_mutex_lock(&icc_bw_lock);
old_avg = path->reqs[0].avg_bw;
old_peak = path->reqs[0].peak_bw;
@@ -730,7 +731,7 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
apply_constraints(path);
}
- mutex_unlock(&icc_bw_lock);
+ rt_mutex_unlock(&icc_bw_lock);
trace_icc_set_bw_end(path, ret);
@@ -939,7 +940,7 @@ void icc_node_add(struct icc_node *node, struct icc_provider *provider)
return;
mutex_lock(&icc_lock);
- mutex_lock(&icc_bw_lock);
+ rt_mutex_lock(&icc_bw_lock);
node->provider = provider;
list_add_tail(&node->node_list, &provider->nodes);
@@ -968,7 +969,7 @@ void icc_node_add(struct icc_node *node, struct icc_provider *provider)
node->avg_bw = 0;
node->peak_bw = 0;
- mutex_unlock(&icc_bw_lock);
+ rt_mutex_unlock(&icc_bw_lock);
mutex_unlock(&icc_lock);
}
EXPORT_SYMBOL_GPL(icc_node_add);
@@ -1094,7 +1095,7 @@ void icc_sync_state(struct device *dev)
return;
mutex_lock(&icc_lock);
- mutex_lock(&icc_bw_lock);
+ rt_mutex_lock(&icc_bw_lock);
synced_state = true;
list_for_each_entry(p, &icc_providers, provider_list) {
dev_dbg(p->dev, "interconnect provider is in synced state\n");
@@ -1107,7 +1108,7 @@ void icc_sync_state(struct device *dev)
}
}
}
- mutex_unlock(&icc_bw_lock);
+ rt_mutex_unlock(&icc_bw_lock);
mutex_unlock(&icc_lock);
}
EXPORT_SYMBOL_GPL(icc_sync_state);