On 11/26/18 6:56 PM, Dr. David Alan Gilbert wrote:
* Xiao Guangrong (guangrong.xiao@xxxxxxxxx) wrote:
On 11/23/18 7:02 PM, Dr. David Alan Gilbert wrote:
+#include "qemu/osdep.h"
+#include "qemu/bitmap.h"
+#include "qemu/threaded-workqueue.h"
+
+#define SMP_CACHE_BYTES 64
That's architecture dependent isn't it?
Yes, it's arch dependent indeed.
I just used 64 for simplification and i think it is <= 64 on most CPU arch-es
so that can work.
Should i introduce statically defined CACHE LINE SIZE for all arch-es? :(
I think it depends why you need it; but we shouldn't have a constant
that is wrong, and we shouldn't define something architecture dependent
in here.
I see. I will address Emilio's suggestion that rename SMP_CACHE_BYTES to
THREAD_QUEUE_ALIGN and additional comments.
+ /*
+ * the bit in these two bitmaps indicates the index of the ＠requests
+ * respectively. If it's the same, the corresponding request is free
+ * and owned by the user, i.e, where the user fills a request. Otherwise,
+ * it is valid and owned by the thread, i.e, where the thread fetches
+ * the request and write the result.
+ */
+
+ /* after the user fills the request, the bit is flipped. */
+ uint64_t request_fill_bitmap QEMU_ALIGNED(SMP_CACHE_BYTES);
+ /* after handles the request, the thread flips the bit. */
+ uint64_t request_done_bitmap QEMU_ALIGNED(SMP_CACHE_BYTES);
Patchew complained about some type mismatches; I think those are because
you're using the bitmap_* functions on these; those functions always
operate on 'long' not on uint64_t - and on some platforms they're
unfortunately not the same.
I guess you were taking about this error:
ERROR: externs should be avoided in .c files
#233: FILE: util/threaded-workqueue.c:65:
+ uint64_t request_fill_bitmap QEMU_ALIGNED(SMP_CACHE_BYTES);
The complained thing is "QEMU_ALIGNED(SMP_CACHE_BYTES)" as it gone
when the aligned thing is removed...
The issue you pointed out can be avoid by using type-casting, like:
bitmap_xor(..., (void *)&thread->request_fill_bitmap)
cannot we?
I thought the error was just due to long vs uint64_t ratehr than the
qemu_aligned. I don't think it's just a casting problem, since I don't
think the long's are always 64bit.
Well, i made some adjustments that makes check_patch.sh really happy :),
as followings:
$ git diff util/
diff --git a/util/threaded-workqueue.c b/util/threaded-workqueue.c
index 2ab37cee8d..e34c65a8eb 100644
--- a/util/threaded-workqueue.c
+++ b/util/threaded-workqueue.c
@@ -62,21 +62,30 @@ struct ThreadLocal {
*/
/* after the user fills the request, the bit is flipped. */
- uint64_t request_fill_bitmap QEMU_ALIGNED(SMP_CACHE_BYTES);
+ struct {
+ uint64_t request_fill_bitmap;
+ } QEMU_ALIGNED(SMP_CACHE_BYTES);
+
/* after handles the request, the thread flips the bit. */
- uint64_t request_done_bitmap QEMU_ALIGNED(SMP_CACHE_BYTES);
+ struct {
+ uint64_t request_done_bitmap;
+ } QEMU_ALIGNED(SMP_CACHE_BYTES);
/*
* the event used to wake up the thread whenever a valid request has
* been submitted
*/
- QemuEvent request_valid_ev QEMU_ALIGNED(SMP_CACHE_BYTES);
+ struct {
+ QemuEvent request_valid_ev;
+ } QEMU_ALIGNED(SMP_CACHE_BYTES);
/*
* the event is notified whenever a request has been completed
* (i.e, become free), which is used to wake up the user
*/
- QemuEvent request_free_ev QEMU_ALIGNED(SMP_CACHE_BYTES);
+ struct {
+ QemuEvent request_free_ev;
+ } QEMU_ALIGNED(SMP_CACHE_BYTES);
};
typedef struct ThreadLocal ThreadLocal;
$ ./scripts/checkpatch.pl -f util/threaded-workqueue.c
total: 0 errors, 0 warnings, 472 lines checked
util/threaded-workqueue.c has no obvious style problems and is ready for submission.
check_patch.sh somehow treats QEMU_ALIGNED as a function before the modification.
And yes, u64 is not a long type on 32 bit arch, it's long[2] instead. that's fine
when we pass the &(u64) to the function whose parameter is (long *). I thing this
trick is widely used. e.g, the example in kvm that i replied to Emilio:
static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu)
{
return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests);
}
