As others pointed, volatile and atomic are slightly different things,
but you have point: atomic operations should probably take volatile
pointers as arguments.
This is what C11 did
http://en.cppreference.com/w/c/atomic/atomic_load
so I do believe that it makes sense to update p_atomic helpers to match
(as one day hopefully we'll replace everything with stdatomic.h)
Jose
On 26/06/15 16:33, Marek Olšák wrote:
I expect the variable will be changed using an atomic operation by the
CPU, or using a coherent store instruction by the GPU.
If this is wrong and volatile is really required here, then
p_atomic_read is wrong too. Should we fix it? For example:
#define p_atomic_read(_v) (*(volatile int*)(_v))
Then, os_wait_until_zero can use p_atomic_read.
Marek
On Fri, Jun 26, 2015 at 4:48 PM, Ilia Mirkin <[email protected]> wrote:
On Fri, Jun 26, 2015 at 7:05 AM, Marek Olšák <[email protected]> wrote:
From: Marek Olšák <[email protected]>
This will be used by radeon and amdgpu winsyses.
Copied from the amdgpu winsys.
---
src/gallium/auxiliary/os/os_time.c | 36 +++++++++++++++++++++++++++++++++++-
src/gallium/auxiliary/os/os_time.h | 10 ++++++++++
2 files changed, 45 insertions(+), 1 deletion(-)
diff --git a/src/gallium/auxiliary/os/os_time.c
b/src/gallium/auxiliary/os/os_time.c
index f7e4ca4..63b6879 100644
--- a/src/gallium/auxiliary/os/os_time.c
+++ b/src/gallium/auxiliary/os/os_time.c
@@ -33,11 +33,12 @@
*/
-#include "pipe/p_config.h"
+#include "pipe/p_defines.h"
#if defined(PIPE_OS_UNIX)
# include <time.h> /* timeval */
# include <sys/time.h> /* timeval */
+# include <sched.h> /* sched_yield */
#elif defined(PIPE_SUBSYSTEM_WINDOWS_USER)
# include <windows.h>
#else
@@ -92,3 +93,36 @@ os_time_sleep(int64_t usecs)
}
#endif
+
+
+bool os_wait_until_zero(int *var, uint64_t timeout)
Does this need to be volatile?
+{
+ if (!*var)
+ return true;
+
+ if (!timeout)
+ return false;
+
+ if (timeout == PIPE_TIMEOUT_INFINITE) {
+ while (*var) {
+#if defined(PIPE_OS_UNIX)
+ sched_yield();
+#endif
+ }
+ return true;
+ }
+ else {
+ int64_t start_time = os_time_get_nano();
+ int64_t end_time = start_time + timeout;
+
+ while (*var) {
+ if (os_time_timeout(start_time, end_time, os_time_get_nano()))
+ return false;
+
+#if defined(PIPE_OS_UNIX)
+ sched_yield();
+#endif
+ }
+ return true;
+ }
+}
diff --git a/src/gallium/auxiliary/os/os_time.h
b/src/gallium/auxiliary/os/os_time.h
index 4fab03c..fdc8040 100644
--- a/src/gallium/auxiliary/os/os_time.h
+++ b/src/gallium/auxiliary/os/os_time.h
@@ -94,6 +94,16 @@ os_time_timeout(int64_t start,
}
+/**
+ * Wait until the variable at the given memory location is zero.
+ *
+ * \param var variable
+ * \param timeout timeout, can be anything from 0 (no wait) to
+ * PIPE_TIME_INFINITE (wait forever)
+ * \return true if the variable is zero
+ */
+bool os_wait_until_zero(int *var, uint64_t timeout);
+
#ifdef __cplusplus
}
#endif
--
2.1.0
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