scsi: fix device removal race vs IO restart callback on resume
There is (mostly theoretical) race between removal of a scsi device and scsi_dma_restart_bh. It used to be easier to hit this race prior to my / Paulo's patch series that added rcu to scsi bus device handling code, but IMHO this race should still be possible to hit, at least in theory. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1854811 Fix it anyway with a patch that was proposed by Paulo in the above bugzilla. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20201210125929.1136390-2-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -170,6 +170,8 @@ static void scsi_dma_restart_bh(void *opaque)
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scsi_req_unref(req);
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scsi_req_unref(req);
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}
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}
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aio_context_release(blk_get_aio_context(s->conf.blk));
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aio_context_release(blk_get_aio_context(s->conf.blk));
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/* Drop the reference that was acquired in scsi_dma_restart_cb */
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object_unref(OBJECT(s));
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}
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}
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void scsi_req_retry(SCSIRequest *req)
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void scsi_req_retry(SCSIRequest *req)
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@ -188,6 +190,8 @@ static void scsi_dma_restart_cb(void *opaque, int running, RunState state)
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}
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}
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if (!s->bh) {
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if (!s->bh) {
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AioContext *ctx = blk_get_aio_context(s->conf.blk);
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AioContext *ctx = blk_get_aio_context(s->conf.blk);
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/* The reference is dropped in scsi_dma_restart_bh.*/
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object_ref(OBJECT(s));
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s->bh = aio_bh_new(ctx, scsi_dma_restart_bh, s);
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s->bh = aio_bh_new(ctx, scsi_dma_restart_bh, s);
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qemu_bh_schedule(s->bh);
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qemu_bh_schedule(s->bh);
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}
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}
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