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coresight: tmc-etr: Allocate and free ETR memory buffers for CPU-wide scenarios

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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>
Tested-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Robert Walker <robert.walker@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mathieu Poirier 2019-04-25 13:53:07 -06:00 committed by Greg Kroah-Hartman
parent c5ff734462
commit 3147da92a8
1 changed files with 104 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

105
drivers/hwtracing/coresight/coresight-tmc-etr.c
View file

@ -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;
@ -1211,6 +1215,72 @@ 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,
@ -1239,7 +1309,8 @@ 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 *
@ -1266,7 +1337,13 @@ 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;
}
@ -1296,9 +1373,33 @@ 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;
if (etr_perf->etr_buf)
tmc_free_etr_buf(etr_perf->etr_buf);
free_etr_perf_buffer:
kfree(etr_perf);
}