Re: [PATCH v3 01/10] Use IDR to maintain all the enabled sources' paths.

Hi,

On Wed, 9 Feb 2022 at 10:57, Mao Jinlong quic_jinlmao@quicinc.com wrote:

Use hash length of the source's device name to map to the pointer of the enabled path. Using IDR will be more efficient than using the list. And there could be other sources except STM and CPU etms in the new HWs. It is better to maintain all the paths together.

Signed-off-by: Mao Jinlong quic_jinlmao@quicinc.com

drivers/hwtracing/coresight/coresight-core.c | 76 +++++++------------- 1 file changed, 27 insertions(+), 49 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 88653d1c06a4..a90097f88425 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -7,6 +7,7 @@ #include <linux/init.h> #include <linux/types.h> #include <linux/device.h> +#include <linux/idr.h> #include <linux/io.h> #include <linux/err.h> #include <linux/export.h> @@ -26,6 +27,12 @@ static DEFINE_MUTEX(coresight_mutex); static DEFINE_PER_CPU(struct coresight_device *, csdev_sink);

+/*

• • Use IDR to map the hash length of the source's device name
• • to the pointer of path for the source
• */

+static DEFINE_IDR(path_idr);

/**

• struct coresight_node - elements of a path, from source to sink
• @csdev: Address of an element.

@@ -36,20 +43,6 @@ struct coresight_node { struct list_head link; };

-/*

• • When operating Coresight drivers from the sysFS interface, only a single
• • path can exist from a tracer (associated to a CPU) to a sink.
• */

-static DEFINE_PER_CPU(struct list_head *, tracer_path);

-/*

• • As of this writing only a single STM can be found in CS topologies. Since
• • there is no way to know if we'll ever see more and what kind of
• • configuration they will enact, for the time being only define a single path
• • for STM.
• */

-static struct list_head *stm_path;

/*

• When losing synchronisation a new barrier packet needs to be inserted at the
• beginning of the data collected in a buffer. That way the decoder knows that

@@ -1088,10 +1081,11 @@ static int coresight_validate_source(struct coresight_device *csdev,

int coresight_enable(struct coresight_device *csdev) {

•   int cpu, ret = 0;
  

•   int ret = 0;
    struct coresight_device *sink;
    struct list_head *path;
    enum coresight_dev_subtype_source subtype;
  

•   u32 hash;
  
    subtype = csdev->subtype.source_subtype;
  
  

@@ -1133,26 +1127,14 @@ int coresight_enable(struct coresight_device *csdev) if (ret) goto err_source;

•   switch (subtype) {
  

•   case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
  

•           /*
  

•            * When working from sysFS it is important to keep track
  

•            * of the paths that were created so that they can be
  

•            * undone in 'coresight_disable()'.  Since there can only
  

•            * be a single session per tracer (when working from sysFS)
  

•            * a per-cpu variable will do just fine.
  

•            */
  

•           cpu = source_ops(csdev)->cpu_id(csdev);
  

•           per_cpu(tracer_path, cpu) = path;
  

•           break;
  

•   case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
  

•           stm_path = path;
  

•           break;
  

•   default:
  

•           /* We can't be here */
  

•           break;
  

•   }
  

•   /*
  

•    * Use the hash length of source's device name as ID
  

Slightly confusing comment: hashlen_string creates a hash and a length for the string. We are using the hash here so comment should be:

"Use the hash of source's device name as ID"

•    * and map the ID to the pointer of the path.
  

•    */
  

•   hash = hashlen_hash(hashlen_string(NULL, dev_name(&csdev->dev)));
  

•   ret = idr_alloc_u32(&path_idr, path, &hash, hash, GFP_KERNEL);
  

•   if (ret)
  

•           goto err_source;
  

out: mutex_unlock(&coresight_mutex); return ret; @@ -1168,8 +1150,9 @@ EXPORT_SYMBOL_GPL(coresight_enable);

void coresight_disable(struct coresight_device *csdev) {

•   int cpu, ret;
  

•   int ret;
    struct list_head *path = NULL;
  

•   u32 hash;
  
    mutex_lock(&coresight_mutex);
  
  

@@ -1180,21 +1163,16 @@ void coresight_disable(struct coresight_device *csdev) if (!csdev->enable || !coresight_disable_source(csdev)) goto out;

•   switch (csdev->subtype.source_subtype) {
  

•   case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
  

•           cpu = source_ops(csdev)->cpu_id(csdev);
  

•           path = per_cpu(tracer_path, cpu);
  

•           per_cpu(tracer_path, cpu) = NULL;
  

•           break;
  

•   case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
  

•           path = stm_path;
  

•           stm_path = NULL;
  

•           break;
  

•   default:
  

•           /* We can't be here */
  

•           break;
  

•   hash = hashlen_hash(hashlen_string(NULL, dev_name(&csdev->dev)));
  

•   /* Find the path by the hash length. */
  

same comment as above re hash / hash length

•   path = idr_find(&path_idr, hash);
  

•   if (path == NULL) {
  

•           dev_info(&csdev->dev, "Path is not found for %s\n",
  

•                           dev_name(&csdev->dev));
  

pr_err() is used in other parts of this file to print error messages.

•           return;
  

this skips the mutex_unlock(). use goto out;

    }

•   idr_remove(&path_idr, hash);
    coresight_disable_path(path);
    coresight_release_path(path);
  
  

-- 2.17.1

Regards

Mike