From aabbe344dc3ca5f7d8263a02608ba6179e8a4499 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 30 Aug 2019 19:03:25 +0100 Subject: [PATCH] drm/i915: Use RCU for unlocked vm_idr lookup Since i915_address_space is now RCU protected, we can do the vm_idr lookup without taking the vm_idr_mutex, just with the rcu_read_lock() instead. Signed-off-by: Chris Wilson Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20190830180325.7755-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 1f735ca9b173..b8969605f4e8 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -1057,14 +1057,11 @@ static int set_ppgtt(struct drm_i915_file_private *file_priv, if (upper_32_bits(args->value)) return -ENOENT; - err = mutex_lock_interruptible(&file_priv->vm_idr_lock); - if (err) - return err; - + rcu_read_lock(); vm = idr_find(&file_priv->vm_idr, args->value); - if (vm) - i915_vm_get(vm); - mutex_unlock(&file_priv->vm_idr_lock); + if (vm && !kref_get_unless_zero(&vm->ref)) + vm = NULL; + rcu_read_unlock(); if (!vm) return -ENOENT; -- 2.30.2