[edk2] [PATCH v3 09/13] OvmfPkg: QemuVideoDxe: serialize Start() against callbacks

Subject: [edk2] [PATCH v3 09/13] OvmfPkg: QemuVideoDxe: serialize Start() against callbacks

From: Laszlo Ersek <lersek@redhat.com>

To: edk2-devel@lists.sourceforge.net

Date: 2014-03-06 09:25:28

  • 2014-03-06 09:25:28  Laszlo Ersek   [edk2] [PATCH v3 09/13] OvmfPkg: QemuVideoDxe: serialize Start() against callbacks
If Start() succeeds, the callback is only executed when the setup is
complete (on the stack of RestoreTPL()), rather than on the stack of
InstallMultipleProtocolInterfaces(), when the driver setup may yet be
theoretically incomplete.

If Start() fails, the protocol interface will have been uninstalled
(rolled back) by the time the callback runs (again, on the stack of
RestoreTPL()). Since protocol notification callbacks begin with locating
the protocol interface in question, such attempts to locate will fail
immediately and save some work in the callback.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek 
---
 OvmfPkg/QemuVideoDxe/Driver.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/QemuVideoDxe/Driver.c b/OvmfPkg/QemuVideoDxe/Driver.c
index e71af6e..c44b8b2 100644
--- a/OvmfPkg/QemuVideoDxe/Driver.c
+++ b/OvmfPkg/QemuVideoDxe/Driver.c
@@ -170,6 +170,7 @@ QemuVideoControllerDriverStart (
   IN EFI_DEVICE_PATH_PROTOCOL       *RemainingDevicePath
   )
 {
+  EFI_TPL                           OldTpl;
   EFI_STATUS                        Status;
   QEMU_VIDEO_PRIVATE_DATA           *Private;
   EFI_DEVICE_PATH_PROTOCOL          *ParentDevicePath;
@@ -178,12 +179,15 @@ QemuVideoControllerDriverStart (
   QEMU_VIDEO_CARD                   *Card;
   EFI_PCI_IO_PROTOCOL               *ChildPciIo;
 
+  OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
+
   //
   // Allocate Private context data for GOP inteface.
   //
   Private = AllocateZeroPool (sizeof (QEMU_VIDEO_PRIVATE_DATA));
   if (Private == NULL) {
-    return EFI_OUT_OF_RESOURCES;
+    Status = EFI_OUT_OF_RESOURCES;
+    goto RestoreTpl;
   }
 
   //
@@ -394,6 +398,7 @@ QemuVideoControllerDriverStart (
     goto UninstallGop;
   }
 
+  gBS->RestoreTPL (OldTpl);
   return EFI_SUCCESS;
 
 UninstallGop:
@@ -424,6 +429,9 @@ ClosePciIo:
 FreePrivate:
   FreePool (Private);
 
+RestoreTpl:
+  gBS->RestoreTPL (OldTpl);
+
   return Status;
 }
 
-- 
1.8.3.1



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