We want to only take the BKL on crap drivers, but to know whether
we have a crap driver we first need to look it up. Split this shuffle
out from the main BKL-disabling patch, for more clarity. Historical
aside: When the kernel-wide BKL was removed, it was replaced by
drm_global_mutex within the scope of the drm subsystem hence why these
two things are (almost) interchangeable as concepts here.
Since the minors are refcounted drm_minor_acquire is purely internal
and this does not have a driver visible effect.
v2: Push the locking even further into drm_open(), suggested by Chris.
This gives us more symmetry with drm_release(), and maybe a futuer
avenue where we make drm_global_mutex locking (partially) opt-in like
with drm_release_noglobal().
v3:
- Actually push this stuff correctly, don't unlock twice (Chris)
- Fix typo on commit message, plus explain why BKL = drm_global_mutex
(Sam)
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
drivers/gpu/drm/drm_drv.c | 14 +++++---------
drivers/gpu/drm/drm_file.c | 6 ++++++
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 8deff75b484c..05bdf0b9d2b3 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -1085,17 +1085,14 @@ static int drm_stub_open(struct inode *inode, struct file *filp)
DRM_DEBUG("\n");
- mutex_lock(&drm_global_mutex);
minor = drm_minor_acquire(iminor(inode));
- if (IS_ERR(minor)) {
- err = PTR_ERR(minor);
- goto out_unlock;
- }
+ if (IS_ERR(minor))
+ return PTR_ERR(minor);
new_fops = fops_get(minor->dev->driver->fops);
if (!new_fops) {
err = -ENODEV;
- goto out_release;
+ goto out;
}
replace_fops(filp, new_fops);
@@ -1104,10 +1101,9 @@ static int drm_stub_open(struct inode *inode, struct file *filp)
else
err = 0;
-out_release:
+out:
drm_minor_release(minor);
-out_unlock:
- mutex_unlock(&drm_global_mutex);
+
return err;
}
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index 1075b3a8b5b1..80d556402ab4 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -378,6 +378,8 @@ int drm_open(struct inode *inode, struct file *filp)
if (IS_ERR(minor))
return PTR_ERR(minor);
+ mutex_lock(&drm_global_mutex);
+
dev = minor->dev;
if (!atomic_fetch_inc(&dev->open_count))
need_setup = 1;
@@ -395,10 +397,14 @@ int drm_open(struct inode *inode, struct file *filp)
goto err_undo;
}
}
+
+ mutex_unlock(&drm_global_mutex);
+
return 0;
err_undo:
atomic_dec(&dev->open_count);
+ mutex_unlock(&drm_global_mutex);
drm_minor_release(minor);
return retcode;
}
--
2.24.1
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