drm/i915: Annotate dma_fence waits
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Message ID 20181106135527.28354-1-daniel.vetter@ffwll.ch
State New
Headers show
Series
  • drm/i915: Annotate dma_fence waits
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Commit Message

Daniel Vetter Nov. 6, 2018, 1:55 p.m. UTC
i915_request_wait is simply our i915-optimized version of
dma_fence_wait. They both use the exact same code. To help lockdep
discovering all the dependencies, annotate it.

v2: We do opportunistic retiring of dma-fences while holding
struct_mutex. The recursion this causes is intentional, and we do have
other paths which (hopefully) do depend upon the struct_mutex. 2nd
option to fix these annotations (and probably even better) would be
creating a dma_fence_signal_opportunistic, which doesnt have the
lockdep annotations. But that also doesn't guarantee that we'll
actually manage to signal fences without depending upon struct_mutex
somewhere, so might as well go with this trick here.

Aside, for non-i915 people: struct_mutex is our bkl. The locking rules
are ... complicated.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/i915_request.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

Comments

kbuild test robot Nov. 6, 2018, 4:48 p.m. UTC | #1
Hi Daniel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on v4.20-rc1 next-20181106]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Daniel-Vetter/drm-i915-Annotate-dma_fence-waits/20181106-232827
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: i386-randconfig-x000-201844 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   drivers/gpu//drm/i915/i915_request.c: In function 'i915_request_wait':
>> drivers/gpu//drm/i915/i915_request.c:1292:3: error: implicit declaration of function 'dma_fence_wait_acquire'; did you mean 'dma_fence_wait_timeout'? [-Werror=implicit-function-declaration]
      dma_fence_wait_acquire();
      ^~~~~~~~~~~~~~~~~~~~~~
      dma_fence_wait_timeout
>> drivers/gpu//drm/i915/i915_request.c:1295:3: error: implicit declaration of function 'dma_fence_wait_release'; did you mean 'dma_fence_release'? [-Werror=implicit-function-declaration]
      dma_fence_wait_release();
      ^~~~~~~~~~~~~~~~~~~~~~
      dma_fence_release
   cc1: some warnings being treated as errors

vim +1292 drivers/gpu//drm/i915/i915_request.c

  1265	
  1266	/**
  1267	 * i915_request_wait - wait until execution of request has finished
  1268	 * @rq: the request to wait upon
  1269	 * @flags: how to wait
  1270	 * @timeout: how long to wait in jiffies
  1271	 *
  1272	 * i915_request_wait() waits for the request to be completed, for a
  1273	 * maximum of @timeout jiffies (with MAX_SCHEDULE_TIMEOUT implying an
  1274	 * unbounded wait).
  1275	 *
  1276	 * If the caller holds the struct_mutex, the caller must pass I915_WAIT_LOCKED
  1277	 * in via the flags, and vice versa if the struct_mutex is not held, the caller
  1278	 * must not specify that the wait is locked.
  1279	 *
  1280	 * Returns the remaining time (in jiffies) if the request completed, which may
  1281	 * be zero or -ETIME if the request is unfinished after the timeout expires.
  1282	 * May return -EINTR is called with I915_WAIT_INTERRUPTIBLE and a signal is
  1283	 * pending before the request completes.
  1284	 */
  1285	long i915_request_wait(struct i915_request *rq,
  1286			       unsigned int flags,
  1287			       long timeout)
  1288	{
  1289		long ret;
  1290	
  1291		if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
> 1292			dma_fence_wait_acquire();
  1293		ret = __i915_request_wait(rq, flags, timeout);
  1294		if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
> 1295			dma_fence_wait_release();
  1296	
  1297		return ret;
  1298	}
  1299	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
kbuild test robot Nov. 6, 2018, 4:48 p.m. UTC | #2
Hi Daniel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on v4.20-rc1 next-20181106]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Daniel-Vetter/drm-i915-Annotate-dma_fence-waits/20181106-232827
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: x86_64-randconfig-x016-201844 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/gpu//drm/i915/i915_request.c: In function 'i915_request_wait':
>> drivers/gpu//drm/i915/i915_request.c:1291:7: error: implicit declaration of function 'lockdep_is_held'; did you mean 'lockdep_assert_held'? [-Werror=implicit-function-declaration]
     if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
          ^~~~~~~~~~~~~~~
          lockdep_assert_held
   drivers/gpu//drm/i915/i915_request.c:1292:3: error: implicit declaration of function 'dma_fence_wait_acquire'; did you mean 'dma_fence_wait_timeout'? [-Werror=implicit-function-declaration]
      dma_fence_wait_acquire();
      ^~~~~~~~~~~~~~~~~~~~~~
      dma_fence_wait_timeout
   drivers/gpu//drm/i915/i915_request.c:1295:3: error: implicit declaration of function 'dma_fence_wait_release'; did you mean 'dma_fence_release'? [-Werror=implicit-function-declaration]
      dma_fence_wait_release();
      ^~~~~~~~~~~~~~~~~~~~~~
      dma_fence_release
   cc1: some warnings being treated as errors

vim +1291 drivers/gpu//drm/i915/i915_request.c

  1265	
  1266	/**
  1267	 * i915_request_wait - wait until execution of request has finished
  1268	 * @rq: the request to wait upon
  1269	 * @flags: how to wait
  1270	 * @timeout: how long to wait in jiffies
  1271	 *
  1272	 * i915_request_wait() waits for the request to be completed, for a
  1273	 * maximum of @timeout jiffies (with MAX_SCHEDULE_TIMEOUT implying an
  1274	 * unbounded wait).
  1275	 *
  1276	 * If the caller holds the struct_mutex, the caller must pass I915_WAIT_LOCKED
  1277	 * in via the flags, and vice versa if the struct_mutex is not held, the caller
  1278	 * must not specify that the wait is locked.
  1279	 *
  1280	 * Returns the remaining time (in jiffies) if the request completed, which may
  1281	 * be zero or -ETIME if the request is unfinished after the timeout expires.
  1282	 * May return -EINTR is called with I915_WAIT_INTERRUPTIBLE and a signal is
  1283	 * pending before the request completes.
  1284	 */
  1285	long i915_request_wait(struct i915_request *rq,
  1286			       unsigned int flags,
  1287			       long timeout)
  1288	{
  1289		long ret;
  1290	
> 1291		if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
  1292			dma_fence_wait_acquire();
  1293		ret = __i915_request_wait(rq, flags, timeout);
  1294		if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
  1295			dma_fence_wait_release();
  1296	
  1297		return ret;
  1298	}
  1299	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 71107540581d..0f800b8967a4 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -30,6 +30,10 @@ 
 
 #include "i915_drv.h"
 
+static long __i915_request_wait(struct i915_request *rq,
+				unsigned int flags,
+				long timeout);
+
 static const char *i915_fence_get_driver_name(struct dma_fence *fence)
 {
 	return "i915";
@@ -66,7 +70,7 @@  static signed long i915_fence_wait(struct dma_fence *fence,
 				   bool interruptible,
 				   signed long timeout)
 {
-	return i915_request_wait(to_request(fence), interruptible, timeout);
+	return __i915_request_wait(to_request(fence), interruptible, timeout);
 }
 
 static void i915_fence_release(struct dma_fence *fence)
@@ -1201,6 +1205,21 @@  static bool __i915_wait_request_check_and_reset(struct i915_request *request)
 long i915_request_wait(struct i915_request *rq,
 		       unsigned int flags,
 		       long timeout)
+{
+	long ret;
+
+	if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
+		dma_fence_wait_acquire();
+	ret = __i915_request_wait(rq, flags, timeout);
+	if (!lockdep_is_held(&rq->i915->drm.struct_mutex))
+		dma_fence_wait_release();
+
+	return ret;
+}
+
+static long __i915_request_wait(struct i915_request *rq,
+				unsigned int flags,
+				long timeout)
 {
 	const int state = flags & I915_WAIT_INTERRUPTIBLE ?
 		TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;