[Qemu-devel] ahci: crash after duplicate bh registration

[Jan Kiszka]

Hi Alex,

I've seen crashes caused by ahci_check_cmd_bh unregistering a NULL bh.
It looks like ahci_dma_set_inactive can a called while there is already
a bh hanging around. Patch below cures the issue, but I have no clue if
such an invocation order is valid at all.

Jan

---

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index e2ed2ad..7870030 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -1066,9 +1066,11 @@ static int ahci_dma_set_inactive(IDEDMA *dma)
 
     ad->dma_cb = NULL;
 
-    /* maybe we still have something to process, check later */
-    ad->check_bh = qemu_bh_new(ahci_check_cmd_bh, ad);
-    qemu_bh_schedule(ad->check_bh);
+    if (!ad->check_bh) {
+        /* maybe we still have something to process, check later */
+        ad->check_bh = qemu_bh_new(ahci_check_cmd_bh, ad);
+        qemu_bh_schedule(ad->check_bh);
+    }
 
     return 0;
 }

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