This patch uses the PID of the process being traced to allocate and free ETR memory buffers for CPU-wide scenarios. The implementation is tailored to handle both N:1 and 1:1 source/sink HW topologies.
Signed-off-by: Mathieu Poirier mathieu.poirier@linaro.org --- .../hwtracing/coresight/coresight-tmc-etr.c | 107 +++++++++++++++++- 1 file changed, 104 insertions(+), 3 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 1346474ac019..61110ef41d00 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -8,6 +8,8 @@ #include <linux/coresight.h> #include <linux/dma-mapping.h> #include <linux/iommu.h> +#include <linux/idr.h> +#include <linux/mutex.h> #include <linux/refcount.h> #include <linux/slab.h> #include <linux/types.h> @@ -26,6 +28,7 @@ struct etr_flat_buf {
/* * etr_perf_buffer - Perf buffer used for ETR + * @drvdata - The ETR drvdaga this buffer has been allocated for. * @etr_buf - Actual buffer used by the ETR * @pid - The PID this etr_perf_buffer belongs to. * @snaphost - Perf session mode @@ -34,6 +37,7 @@ struct etr_flat_buf { * @pages - Array of Pages in the ring buffer. */ struct etr_perf_buffer { + struct tmc_drvdata *drvdata; struct etr_buf *etr_buf; pid_t pid; bool snapshot; @@ -1210,6 +1214,72 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event, return etr_buf; }
+static struct etr_buf * +get_perf_etr_buf_cpu_wide(struct tmc_drvdata *drvdata, + struct perf_event *event, int nr_pages, + void **pages, bool snapshot) +{ + int ret; + pid_t pid = task_pid_nr(event->owner); + struct etr_buf *etr_buf; + +retry: + /* + * An etr_perf_buffer is associated with an event and holds a reference + * to the AUX ring buffer that was created for that event. In CPU-wide + * N:1 mode multiple events (one per CPU), each with its own AUX ring + * buffer, share a sink. As such an etr_perf_buffer is created for each + * event but a single etr_buf associated with the ETR is shared between + * them. The last event in a trace session will copy the content of the + * etr_buf to its AUX ring buffer. Ring buffer associated to other + * events are simply not used an freed as events are destoyed. We still + * need to allocate a ring buffer for each event since we don't know + * which event will be last. + */ + + /* + * The first thing to do here is check if an etr_buf has already been + * allocated for this session. If so it is shared with this event, + * otherwise it is created. + */ + mutex_lock(&drvdata->idr_mutex); + etr_buf = idr_find(&drvdata->idr, pid); + if (etr_buf) { + refcount_inc(&etr_buf->refcount); + mutex_unlock(&drvdata->idr_mutex); + return etr_buf; + } + + /* If we made it here no buffer has been allocated, do so now. */ + mutex_unlock(&drvdata->idr_mutex); + + etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot); + if (IS_ERR(etr_buf)) + return etr_buf; + + refcount_set(&etr_buf->refcount, 1); + + /* Now that we have a buffer, add it to the IDR. */ + mutex_lock(&drvdata->idr_mutex); + ret = idr_alloc(&drvdata->idr, etr_buf, pid, pid + 1, GFP_KERNEL); + mutex_unlock(&drvdata->idr_mutex); + + /* Another event with this session ID has allocated this buffer. */ + if (ret == -ENOSPC) { + tmc_free_etr_buf(etr_buf); + goto retry; + } + + /* The IDR can't allocate room for a new session, abandon ship. */ + if (ret == -ENOMEM) { + tmc_free_etr_buf(etr_buf); + return ERR_PTR(ret); + } + + + return etr_buf; +} + static struct etr_buf * get_perf_etr_buf_per_thread(struct tmc_drvdata *drvdata, struct perf_event *event, int nr_pages, @@ -1238,7 +1308,8 @@ get_perf_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event, return get_perf_etr_buf_per_thread(drvdata, event, nr_pages, pages, snapshot);
- return ERR_PTR(-ENOENT); + return get_perf_etr_buf_cpu_wide(drvdata, event, nr_pages, + pages, snapshot); }
static struct etr_perf_buffer * @@ -1265,7 +1336,13 @@ tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, struct perf_event *event, return ERR_PTR(-ENOMEM);
done: + /* + * Keep a reference to the ETR this buffer has been allocated for + * in order to have access to the IDR in tmc_free_etr_buffer(). + */ + etr_perf->drvdata = drvdata; etr_perf->etr_buf = etr_buf; + return etr_perf; }
@@ -1295,9 +1372,33 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev, static void tmc_free_etr_buffer(void *config) { struct etr_perf_buffer *etr_perf = config; + struct tmc_drvdata *drvdata = etr_perf->drvdata; + struct etr_buf *buf, *etr_buf = etr_perf->etr_buf; + + if (!etr_buf) + goto free_etr_perf_buffer; + + mutex_lock(&drvdata->idr_mutex); + /* If we are not the last one to use the buffer, don't touch it. */ + if (!refcount_dec_and_test(&etr_buf->refcount)) { + mutex_unlock(&drvdata->idr_mutex); + goto free_etr_perf_buffer; + } + + /* We are the last one, remove from the IDR and free the buffer. */ + buf = idr_remove(&drvdata->idr, etr_perf->pid); + mutex_unlock(&drvdata->idr_mutex); + + /* + * Something went very wrong if the buffer associated with this ID + * is not the same in the IDR. Leak to avoid use after free. + */ + if (buf && WARN_ON(buf != etr_buf)) + goto free_etr_perf_buffer; + + tmc_free_etr_buf(etr_perf->etr_buf);
- if (etr_perf->etr_buf) - tmc_free_etr_buf(etr_perf->etr_buf); +free_etr_perf_buffer: kfree(etr_perf); }