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authorTvrtko Ursulin <tvrtko.ursulin@intel.com>2023-06-21 12:48:24 +0300
committerChristian König <christian.koenig@amd.com>2023-09-20 16:27:44 +0300
commit1c7a387ffef894b1ab3942f0482dac7a6e0a909c (patch)
treee0d636830690c6d858691cb8c93b6ced37407b5e /drivers/gpu/drm/drm_ioctl.c
parent9fc75c40faa29df14ba16066be6bdfaea9f39ce4 (diff)
downloadlinux-1c7a387ffef894b1ab3942f0482dac7a6e0a909c.tar.xz
drm: Update file owner during use
With the typical model where the display server opens the file descriptor and then hands it over to the client(*), we were showing stale data in debugfs. Fix it by updating the drm_file->pid on ioctl access from a different process. The field is also made RCU protected to allow for lockless readers. Update side is protected with dev->filelist_mutex. Before: $ cat /sys/kernel/debug/dri/0/clients command pid dev master a uid magic Xorg 2344 0 y y 0 0 Xorg 2344 0 n y 0 2 Xorg 2344 0 n y 0 3 Xorg 2344 0 n y 0 4 After: $ cat /sys/kernel/debug/dri/0/clients command tgid dev master a uid magic Xorg 830 0 y y 0 0 xfce4-session 880 0 n y 0 1 xfwm4 943 0 n y 0 2 neverball 1095 0 n y 0 3 *) More detailed and historically accurate description of various handover implementation kindly provided by Emil Velikov: """ The traditional model, the server was the orchestrator managing the primary device node. From the fd, to the master status and authentication. But looking at the fd alone, this has varied across the years. IIRC in the DRI1 days, Xorg (libdrm really) would have a list of open fd(s) and reuse those whenever needed, DRI2 the client was responsible for open() themselves and with DRI3 the fd was passed to the client. Around the inception of DRI3 and systemd-logind, the latter became another possible orchestrator. Whereby Xorg and Wayland compositors could ask it for the fd. For various reasons (hysterical and genuine ones) Xorg has a fallback path going the open(), whereas Wayland compositors are moving to solely relying on logind... some never had fallback even. Over the past few years, more projects have emerged which provide functionality similar (be that on API level, Dbus, or otherwise) to systemd-logind. """ v2: * Fixed typo in commit text and added a fine historical explanation from Emil. Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: "Christian König" <christian.koenig@amd.com> Cc: Daniel Vetter <daniel@ffwll.ch> Acked-by: Christian König <christian.koenig@amd.com> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> Reviewed-by: Rob Clark <robdclark@gmail.com> Tested-by: Rob Clark <robdclark@gmail.com> Link: https://patchwork.freedesktop.org/patch/msgid/20230621094824.2348732-1-tvrtko.ursulin@linux.intel.com Signed-off-by: Christian König <christian.koenig@amd.com>
Diffstat (limited to 'drivers/gpu/drm/drm_ioctl.c')
-rw-r--r--drivers/gpu/drm/drm_ioctl.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index f03ffbacfe9b..77590b0f38fa 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -776,6 +776,9 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata,
struct drm_device *dev = file_priv->minor->dev;
int retcode;
+ /* Update drm_file owner if fd was passed along. */
+ drm_file_update_pid(file_priv);
+
if (drm_dev_is_unplugged(dev))
return -ENODEV;