[Qemu-devel] [PATCH] make pci_bridge_region_cleanup to be done in rcu queue after flatview_destroy.

[QiaoChong]

pci_bridge_region_cleanup need to done after flatview_destroy,
because memory_region_unref need access memory regions in PCIBridgeWindows in 
flatview_destroy.
here we delay pci_bridge_region_cleanup to be done in rcu queue work.

bellow are gdb backtraces.

oldcode mr->name will be freed in object_unparent, before flatview_destroy.

    mask=<optimized out>, attrs=...) at 
/work/work/loongson/qemu/qemu-latest/memory.c:559
    access_size_min=<optimized out>, access_size_max=<optimized out>, 
access_fn=0x555555876850 <memory_region_write_accessor>,
    mr=0x5555569608c0, attrs=...) at 
/work/work/loongson/qemu/qemu-latest/memory.c:626
    at /work/work/loongson/qemu/qemu-latest/memory.c:1518
    address@hidden "", address@hidden, addr1=4, l=4, mr=0x5555569608c0) at 
/work/work/loongson/qemu/qemu-latest/exec.c:3255
    at /work/work/loongson/qemu/qemu-latest/exec.c:3294
    at /work/work/loongson/qemu/qemu-latest/exec.c:2910
    shift=<optimized out>, mask=<optimized out>, attrs=...) at 
/work/work/loongson/qemu/qemu-latest/memory.c:585
    access_size_min=<optimized out>, access_size_max=<optimized out>, 
access_fn=0x555555874700 <memory_region_write_with_attrs_accessor>,
    mr=0x555557338120, attrs=...) at 
/work/work/loongson/qemu/qemu-latest/memory.c:626
    address@hidden, attrs=...) at 
/work/work/loongson/qemu/qemu-latest/memory.c:1518
    address@hidden, address@hidden, address@hidden, recheck=false, size=4)
    at /work/work/loongson/qemu/qemu-latest/accel/tcg/cputlb.c:905
    mmu_idx=<optimized out>, env=0x55555681d218) at 
/work/work/loongson/qemu/qemu-latest/accel/tcg/softmmu_template.h:268
    at /work/work/loongson/qemu/qemu-latest/accel/tcg/softmmu_template.h:304
    at /work/work/loongson/qemu/qemu-latest/accel/tcg/cpu-exec.c:171
    at /work/work/loongson/qemu/qemu-latest/accel/tcg/cpu-exec.c:612

here mr mr->owner, mr->name has been freed in object_unparent before.

void memory_region_unref(MemoryRegion *mr)
{
    if (mr && mr->owner) {
        object_unref(mr->owner);
    }
}

Signed-off-by: QiaoChong <address@hidden>
---
 hw/pci/pci_bridge.c         | 12 +++++++++++-
 include/hw/pci/pci_bridge.h |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
index 40a39f5..a3c9501 100644
--- a/hw/pci/pci_bridge.c
+++ b/hw/pci/pci_bridge.c
@@ -233,6 +233,16 @@ static void pci_bridge_region_cleanup(PCIBridge *br, 
PCIBridgeWindows *w)
     g_free(w);
 }
 
+/*
+pci_bridge_region_cleanup need to done after flatview_destroy,
+because memory_region_unref need access memory regions in PCIBridgeWindows in 
flatview_destroy.
+here we delay pci_bridge_region_cleanup to be done in rcu queue work.
+*/
+static void pci_bridge_region_cleanup_schedule(PCIBridgeWindows *w)
+{
+  pci_bridge_region_cleanup(NULL, w);
+}
+
 void pci_bridge_update_mappings(PCIBridge *br)
 {
     PCIBridgeWindows *w = br->windows;
@@ -243,7 +253,7 @@ void pci_bridge_update_mappings(PCIBridge *br)
     pci_bridge_region_del(br, br->windows);
     br->windows = pci_bridge_region_init(br);
     memory_region_transaction_commit();
-    pci_bridge_region_cleanup(br, w);
+    call_rcu(w,  pci_bridge_region_cleanup_schedule, rcu);
 }
 
 /* default write_config function for PCI-to-PCI bridge */
diff --git a/include/hw/pci/pci_bridge.h b/include/hw/pci/pci_bridge.h
index 0347da5..0e1fd82 100644
--- a/include/hw/pci/pci_bridge.h
+++ b/include/hw/pci/pci_bridge.h
@@ -37,6 +37,7 @@ typedef struct PCIBridgeWindows PCIBridgeWindows;
  * as subregions.
  */
 struct PCIBridgeWindows {
+    struct rcu_head rcu;
     MemoryRegion alias_pref_mem;
     MemoryRegion alias_mem;
     MemoryRegion alias_io;
-- 
2.7.4