[win-pv-devel] [PATCH] Fix race setting SrbStatus

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

SrbStatus needs to be set to PENDING right at the beginning of the
prepare functions, before the SRB has been added to any queue, otherwise
we risk a race with the completion code.

Reported-by: Andreas Kinzler <ml-ak@xxxxxxxxx>
Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
 src/xenvbd/pdo.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/xenvbd/pdo.c b/src/xenvbd/pdo.c
index ee2a3cc..3ce48cc 100644
--- a/src/xenvbd/pdo.c
+++ b/src/xenvbd/pdo.c
@@ -1171,6 +1171,8 @@ PrepareReadWrite(
     XENVBD_SG_LIST  SGList;
     ULONG           DebugCount;
 
+    Srb->SrbStatus = SRB_STATUS_PENDING;
+
     InitializeListHead(&List);
     SrbExt->Count = 0;
 
@@ -1213,7 +1215,6 @@ PrepareReadWrite(
     if (DebugCount != (ULONG)SrbExt->Count) {
         Trace("[%u] %d != %u\n", PdoGetTargetId(Pdo), SrbExt->Count, 
DebugCount);
     }
-    Srb->SrbStatus = SRB_STATUS_PENDING;
     return TRUE;
 
 fail3:
@@ -1237,6 +1238,8 @@ PrepareSyncCache(
     LIST_ENTRY          List;
     UCHAR               Operation;
     ULONG               DebugCount;
+
+    Srb->SrbStatus = SRB_STATUS_PENDING;
     
     if (FrontendGetDiskInfo(Pdo->Frontend)->FlushCache)
         Operation = BLKIF_OP_FLUSH_DISKCACHE;
@@ -1260,7 +1263,6 @@ PrepareSyncCache(
     if (DebugCount != (ULONG)SrbExt->Count) {
         Trace("[%u] %d != %u\n", PdoGetTargetId(Pdo), SrbExt->Count, 
DebugCount);
     }
-    Srb->SrbStatus = SRB_STATUS_PENDING;
     return TRUE;
 
 fail1:
@@ -1284,6 +1286,8 @@ PrepareUnmap(
     LIST_ENTRY          List;
     ULONG               DebugCount;
 
+    Srb->SrbStatus = SRB_STATUS_PENDING;
+
     InitializeListHead(&List);
     SrbExt->Count = 0;
 
@@ -1308,7 +1312,6 @@ PrepareUnmap(
     if (DebugCount != (ULONG)SrbExt->Count) {
         Trace("[%u] %d != %u\n", PdoGetTargetId(Pdo), SrbExt->Count, 
DebugCount);
     }
-    Srb->SrbStatus = SRB_STATUS_PENDING;
     return TRUE;
 
 fail1:
-- 
2.5.3


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