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libdrm/iris: make locking more fine grained

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When more than one thread are accessing the DRM interface it is not wise
to use global locking, especially when a pthread is executing a batch
buffer and waits for a completion signal in the VFS-plugin. In case the
EP gets stuck in the global lock, no progress is made. Therefore:

* use _drm_mutex only where strictly necessary
* use special _exec_mutex to protect buffer execution (per context)
* print warning when two threads try to execute a buffer in the same
  context

isse #5224
This commit is contained in:
Sebastian Sumpf 2024-05-23 19:50:24 +02:00 committed by Christian Helmuth
parent f79ff59619
commit 179b3eb7e4
1 changed files with 37 additions and 6 deletions
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43
repos/libports/src/lib/libdrm/ioctl_iris.cc
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@ -352,7 +352,6 @@ struct Drm::Buffer
Drm::Buffer_id id() const
{
/* skip first id (0) */
return Drm::Buffer_id { _elem.id().value };
}
};
@ -586,9 +585,32 @@ struct Drm::Context
} catch (Buffer::Id_space::Unknown_id) { }
}
Genode::Mutex _exec_mutex { };
unsigned _exec_counter { 0 };
struct Exec_mutex_check
{
unsigned &_counter;
Exec_mutex_check(unsigned &counter)
: _counter(counter)
{
_counter++;
}
~Exec_mutex_check() { _counter--; }
};
int exec_buffer(drm_i915_gem_exec_object2 *obj, uint64_t count,
uint64_t batch_id, size_t batch_length)
{
if (_exec_counter > 0)
Genode::warning("Parallel calls to '", __func__, "' are ",
"unsupported. This call may block forever");
Genode::Mutex::Guard guard { _exec_mutex };
Exec_mutex_check exec_guard { _exec_counter };
Buffer *command_buffer = nullptr;
for (uint64_t i = 0; i < count; i++) {
@ -784,6 +806,8 @@ class Drm::Call
int _device_gem_create(void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
auto const p = reinterpret_cast<drm_i915_gem_create*>(arg);
uint64_t const size = (p->size + 0xfff) & ~0xfff;
@ -804,6 +828,8 @@ class Drm::Call
int _device_gem_mmap(void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
auto const p = reinterpret_cast<drm_i915_gem_mmap *>(arg);
Drm::Buffer_id const id { .value = p->handle };
@ -938,6 +964,8 @@ class Drm::Call
int _device_gem_context_create(void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
drm_i915_gem_context_create * const p = reinterpret_cast<drm_i915_gem_context_create*>(arg);
int fd = Libc::open("/dev/gpu", 0);
@ -971,6 +999,8 @@ class Drm::Call
int _device_gem_context_destroy(void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
unsigned long ctx_id = reinterpret_cast<drm_i915_gem_context_destroy *>(arg)->ctx_id;
Context_id const id = Drm::Context::id(ctx_id);
@ -1224,6 +1254,8 @@ class Drm::Call
int _generic_gem_close(void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
auto const p = reinterpret_cast<drm_gem_close*>(arg);
Drm::Buffer_id const id { .value = p->handle };
return _free_buffer(id);
@ -1425,9 +1457,6 @@ class Drm::Call
drm_syncobj_create reserve_id_0 { };
if (_generic_syncobj_create(&reserve_id_0))
Genode::warning("syncobject 0 not reserved");
/* make handle id 0 unavailable in buffer space */
_alloc_buffer(0x1000, [](Buffer &) { });
}
~Call()
@ -1460,6 +1489,8 @@ class Drm::Call
void unmap_buffer(void *addr, size_t length)
{
Genode::Mutex::Guard guard { _drm_mutex };
bool found = false;
_buffer_space.for_each<Buffer>([&] (Buffer &b) {
@ -1488,6 +1519,8 @@ class Drm::Call
void unmap_buffer_ppgtt(__u32 handle)
{
Genode::Mutex::Guard guard { _drm_mutex };
Drm::Buffer_id const id = { .value = handle };
_context_space.for_each<Drm::Context>([&](Drm::Context &context) {
context.unmap_buffer_gpu(id);
@ -1496,8 +1529,6 @@ class Drm::Call
int ioctl(unsigned long request, void *arg)
{
Genode::Mutex::Guard guard { _drm_mutex };
bool const device = device_ioctl(request);
return device ? _device_ioctl(device_number(request), arg)
: _generic_ioctl(command_number(request), arg);