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Fix potential deadlock in discard

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HB lock takes inclusive metadata lock, which is taken also by metadata
flush, thus trying to call metadata flush under HB lock attempts to take
this lock recursively. In that case, if in the meantime some other thread
would try to take exclusive metadata lock, the inner inclusive lock would
block (because the lock keeps the order), with outer inclusive lock still
held, leading to a deadlock.

Signed-off-by: Robert Baldyga <robert.baldyga@huawei.com>
This commit is contained in:
Robert Baldyga 2024-03-20 23:11:41 +01:00
parent a7a62cb44a
commit fd489e3a30
1 changed files with 3 additions and 2 deletions
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5
src/engine/engine_discard.c
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@ -1,5 +1,6 @@
/*
* Copyright(c) 2012-2022 Intel Corporation
* Copyright(c) 2024 Huawei Technologies
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "ocf/ocf.h"
@ -152,13 +153,13 @@ int _ocf_discard_step_do(struct ocf_request *req)
/* Remove mapped cache lines from metadata */
ocf_purge_map_info(req);
ocf_hb_req_prot_unlock_wr(req);
if (req->info.flush_metadata) {
/* Request was dirty and need to flush metadata */
ocf_metadata_flush_do_asynch(cache, req,
_ocf_discard_step_complete);
}
ocf_hb_req_prot_unlock_wr(req);
}
ocf_hb_req_prot_lock_rd(req);