From 5c8d420b7c2a26b7153114396e6d0c4c1641dd3d Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Tue, 19 Aug 2008 21:37:16 +0000
Subject: [PATCH] * Added "bool wait" parameter to _GetOperation(). If false
 and no unused   operation is available ATM, it will return NULL. *
 _Finisher() does now re-schedule a request, if all of its operations  
 finished successfully, but there are still remaining bytes. * _Scheduler()
 does now operate in two passes. First it creates as many   operations for a
 given request as possible, then it executes the   operations. This fixes bug
 #2644. The problem was that by creating and   executing the operations in a
 single loop, an operation could be   finished before the next one was added.
 The request would thus be   considered finished and the request owner be
 notified. This would   usually lead to the destruction of the request while
 it was still in   use. * _Scheduler(): In case we don't have a DMA resource
 also advance the   request.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27070 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 .../kernel/device_manager/IOScheduler.cpp     | 26 +++++++++++++++----
 .../kernel/device_manager/IOScheduler.h       |  2 +-
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/system/kernel/device_manager/IOScheduler.cpp b/src/system/kernel/device_manager/IOScheduler.cpp
index 0c7f5b6d5a..e0363bbc7c 100644
--- a/src/system/kernel/device_manager/IOScheduler.cpp
+++ b/src/system/kernel/device_manager/IOScheduler.cpp
@@ -209,7 +209,12 @@ IOScheduler::_Finisher()
 
 		// If the request is done, we need to perform its notifications.
 		if (request->IsFinished()) {
-			if (request->HasCallbacks()) {
+			if (request->Status() == B_OK && request->RemainingBytes() > 0) {
+				// The request has been processed OK so far, but it isn't really
+				// finished yet.
+				fUnscheduledRequests.Add(request);
+				fNewRequestCondition.NotifyAll();
+			} else if (request->HasCallbacks()) {
 				// The request has callbacks that may take some time to perform,
 				// so we hand it over to the request notifier.
 				fFinishedRequests.Add(request);
@@ -233,13 +238,13 @@ IOScheduler::_FinisherWorkPending()
 
 
 IOOperation*
-IOScheduler::_GetOperation()
+IOScheduler::_GetOperation(bool wait)
 {
 	while (true) {
 		MutexLocker locker(fLock);
 
 		IOOperation* operation = fUnusedOperations.RemoveHead();
-		if (operation != NULL)
+		if (operation != NULL || !wait)
 			return operation;
 
 		// Wait for new operations. First check whether any finisher work has
@@ -311,16 +316,26 @@ IOScheduler::_Scheduler()
 		TRACE("IOScheduler::_Scheduler(): request: %p\n", request);
 
 		if (fDMAResource != NULL) {
+			IOOperationList operations;
 			while (request->RemainingBytes() > 0) {
-				IOOperation* operation = _GetOperation();
+				IOOperation* operation = _GetOperation(operations.IsEmpty());
+				if (operation == NULL)
+					break;
 
 				status_t status = fDMAResource->TranslateNext(request,
 					operation);
 				if (status != B_OK) {
+// TODO: Handle correctly! E.g. B_BUSY just means that some resource (e.g.
+// DMA buffers) isn't available ATM. We should execute the operations we have
+// so far and wait for resources to become available again.
 					AbortRequest(request, status);
 					break;
 				}
 
+				operations.Add(operation);
+			}
+
+			while (IOOperation* operation = operations.RemoveHead()) {
 				TRACE("IOScheduler::_Scheduler(): calling callback for "
 					"operation: %p\n", operation);
 
@@ -329,9 +344,10 @@ IOScheduler::_Scheduler()
 		} else {
 // TODO: If the device has block size restrictions, we might need to use a
 // bounce buffer.
-			IOOperation* operation = _GetOperation();
+			IOOperation* operation = _GetOperation(true);
 			operation->Prepare(request);
 			operation->SetOriginalRange(request->Offset(), request->Length());
+			request->Advance(request->Length());
 			fIOCallback(fIOCallbackData, operation);
 		}
 	}
diff --git a/src/system/kernel/device_manager/IOScheduler.h b/src/system/kernel/device_manager/IOScheduler.h
index 0ecf5f978c..e3cb2ed1c0 100644
--- a/src/system/kernel/device_manager/IOScheduler.h
+++ b/src/system/kernel/device_manager/IOScheduler.h
@@ -47,7 +47,7 @@ public:
 private:
 			void				_Finisher();
 			bool				_FinisherWorkPending();
-			IOOperation*		_GetOperation();
+			IOOperation*		_GetOperation(bool wait);
 			IORequest*			_GetNextUnscheduledRequest();
 			status_t			_Scheduler();
 	static	status_t			_SchedulerThread(void* self);