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| author | Christian Schoenebeck <qemu_oss@crudebyte.com> | 2025-03-07 10:22:56 +0100 |
|---|---|---|
| committer | Christian Schoenebeck <qemu_oss@crudebyte.com> | 2025-05-05 11:28:28 +0200 |
| commit | 61da38db70affd925226ce1e8a61d761c20d045b (patch) | |
| tree | 1447c147d327735462719de8d7d40398e068d2ff | |
| parent | 5134cf9b5d3aee4475fe7e1c1c11b093731073cf (diff) | |
| download | qemu-61da38db70affd925226ce1e8a61d761c20d045b.zip qemu-61da38db70affd925226ce1e8a61d761c20d045b.tar.gz qemu-61da38db70affd925226ce1e8a61d761c20d045b.tar.bz2 | |
9pfs: fix concurrent v9fs_reclaim_fd() calls
Even though this function is serialized to be always called from main
thread, v9fs_reclaim_fd() is dispatching the coroutine to a worker thread
in between via its v9fs_co_*() calls, hence leading to the situation where
v9fs_reclaim_fd() is effectively executed multiple times simultaniously,
which renders its LRU algorithm useless and causes high latency.
Fix this by adding a simple boolean variable to ensure this function is
only called once at a time. No synchronization needed for this boolean
variable as this function is only entered and returned on main thread.
Fixes: 7a46274529c ('hw/9pfs: Add file descriptor reclaim support')
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <5c622067efd66dd4ee5eca740dcf263f41db20b2.1741339452.git.qemu_oss@crudebyte.com>
| -rw-r--r-- | hw/9pfs/9p.c | 10 | ||||
| -rw-r--r-- | hw/9pfs/9p.h | 1 |
2 files changed, 11 insertions, 0 deletions
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 7cad2bc..4f9c2dd 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -435,6 +435,12 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu) GHashTableIter iter; gpointer fid; + /* prevent multiple coroutines running this function simultaniously */ + if (s->reclaiming) { + return; + } + s->reclaiming = true; + g_hash_table_iter_init(&iter, s->fids); QSLIST_HEAD(, V9fsFidState) reclaim_list = @@ -510,6 +516,8 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu) */ put_fid(pdu, f); } + + s->reclaiming = false; } /* @@ -4324,6 +4332,8 @@ int v9fs_device_realize_common(V9fsState *s, const V9fsTransport *t, s->ctx.fst = &fse->fst; fsdev_throttle_init(s->ctx.fst); + s->reclaiming = false; + rc = 0; out: if (rc) { diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h index 5e041e1..259ad32 100644 --- a/hw/9pfs/9p.h +++ b/hw/9pfs/9p.h @@ -362,6 +362,7 @@ struct V9fsState { uint64_t qp_ndevices; /* Amount of entries in qpd_table. */ uint16_t qp_affix_next; uint64_t qp_fullpath_next; + bool reclaiming; }; /* 9p2000.L open flags */ |