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Message-ID: <20240501185047.3126832-2-adrian.larumbe@collabora.com>
Date: Wed, 1 May 2024 19:50:43 +0100
From: Adrián Larumbe <adrian.larumbe@...labora.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>
Cc: kernel@...labora.com,
Adrian Larumbe <adrian.larumbe@...labora.com>,
dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org,
Rob Clark <robdclark@...il.com>,
Tvrtko Ursulin <tursulin@...ulin.net>
Subject: [PATCH v2 1/1] drm: Add ioctl for querying a DRM device's list of open client PIDs
Up to this day, all fdinfo-based GPU profilers must traverse the entire
/proc directory structure to find open DRM clients with fdinfo file
descriptors. This is inefficient and time-consuming.
This patch adds a new DRM ioctl that allows users to obtain a list of PIDs
for clients who have opened the DRM device. Output from the ioctl isn't
human-readable, and it's meant to be retrieved only by GPU profilers like
gputop and nvtop.
Cc: Rob Clark <robdclark@...il.com>
Cc: Tvrtko Ursulin <tursulin@...ulin.net>
Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
---
drivers/gpu/drm/drm_internal.h | 1 +
drivers/gpu/drm/drm_ioctl.c | 89 ++++++++++++++++++++++++++++++++++
include/uapi/drm/drm.h | 7 +++
3 files changed, 97 insertions(+)
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 690505a1f7a5..6f78954cae16 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -243,6 +243,7 @@ static inline void drm_debugfs_encoder_remove(struct drm_encoder *encoder)
drm_ioctl_t drm_version;
drm_ioctl_t drm_getunique;
drm_ioctl_t drm_getclient;
+drm_ioctl_t drm_getclients;
/* drm_syncobj.c */
void drm_syncobj_open(struct drm_file *file_private);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index e368fc084c77..da7057376581 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -207,6 +207,93 @@ int drm_getclient(struct drm_device *dev, void *data,
}
}
+/*
+ * Get list of client PIDs who have opened a DRM file
+ *
+ * \param dev DRM device we are querying
+ * \param data IOCTL command input.
+ * \param file_priv DRM file private.
+ *
+ * \return zero on success or a negative number on failure.
+ *
+ * Traverses list of open clients for the given DRM device, and
+ * copies them into userpace as an array of PIDs
+ */
+int drm_getclients(struct drm_device *dev, void *data,
+ struct drm_file *file_priv)
+
+{
+ struct drm_get_clients *get_clients = data;
+ ssize_t size = get_clients->len;
+ char __user *pid_buf;
+ ssize_t offset = 0;
+ int ret = 0;
+
+ /*
+ * We do not want to show clients of display only devices so
+ * as to avoid confusing UM GPU profilers
+ */
+ if (!dev->render) {
+ get_clients->len = 0;
+ return 0;
+ }
+
+ /*
+ * An input size of zero means UM wants to know the size of the PID buffer
+ * We round it up to the nearest multiple of the page size so that we can have
+ * some spare headroom in case more clients came in between successive calls
+ * of this ioctl, and also to simplify parsing of the PIDs buffer, because
+ * sizeof(pid_t) will hopefully always divide PAGE_SIZE
+ */
+ if (size == 0) {
+ get_clients->len =
+ roundup(atomic_read(&dev->open_count) * sizeof(pid_t), PAGE_SIZE);
+ return 0;
+ }
+
+ pid_buf = (char *)(void *)get_clients->user_data;
+
+ if (!pid_buf)
+ return -EINVAL;
+
+ mutex_lock(&dev->filelist_mutex);
+ list_for_each_entry_reverse(file_priv, &dev->filelist, lhead) {
+ pid_t pid_num;
+
+ if ((size - offset) < sizeof(pid_t))
+ break;
+
+ rcu_read_lock();
+ pid_num = pid_vnr(rcu_dereference(file_priv->pid));
+ rcu_read_unlock();
+
+ /* We do not want to return the profiler's PID */
+ if (pid_vnr(task_tgid(current)) == pid_num)
+ continue;
+
+ ret = copy_to_user(pid_buf + offset, &pid_num, sizeof(pid_t));
+ if (ret)
+ break;
+
+ offset += sizeof(pid_t);
+ }
+ mutex_unlock(&dev->filelist_mutex);
+
+ if (ret)
+ return -EFAULT;
+
+ if ((size - offset) >= sizeof(pid_t)) {
+ pid_t pid_zero = 0;
+
+ ret = copy_to_user(pid_buf + offset,
+ &pid_zero, sizeof(pid_t));
+ if (ret)
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
/*
* Get statistics information.
*
@@ -672,6 +759,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
DRM_IOCTL_DEF(DRM_IOCTL_MODE_LIST_LESSEES, drm_mode_list_lessees_ioctl, DRM_MASTER),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_GET_LEASE, drm_mode_get_lease_ioctl, DRM_MASTER),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_REVOKE_LEASE, drm_mode_revoke_lease_ioctl, DRM_MASTER),
+
+ DRM_IOCTL_DEF(DRM_IOCTL_GET_CLIENTS, drm_getclients, DRM_RENDER_ALLOW),
};
#define DRM_CORE_IOCTL_COUNT ARRAY_SIZE(drm_ioctls)
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 16122819edfe..c47aa9de51ab 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -1024,6 +1024,11 @@ struct drm_crtc_queue_sequence {
__u64 user_data; /* user data passed to event */
};
+struct drm_get_clients {
+ __u64 user_data;
+ __kernel_size_t len;
+};
+
#if defined(__cplusplus)
}
#endif
@@ -1236,6 +1241,8 @@ extern "C" {
#define DRM_IOCTL_SYNCOBJ_TRANSFER DRM_IOWR(0xCC, struct drm_syncobj_transfer)
#define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL DRM_IOWR(0xCD, struct drm_syncobj_timeline_array)
+#define DRM_IOCTL_GET_CLIENTS DRM_IOWR(0xD1, struct drm_get_clients)
+
/**
* DRM_IOCTL_MODE_GETFB2 - Get framebuffer metadata.
*
--
2.44.0
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