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| author | Dave Jiang <dave.jiang@intel.com> | 2023-11-17 13:18:48 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-01-10 17:17:02 +0100 |
| commit | 0a460481df435f955d569b44e7674ff81dfc7f74 (patch) | |
| tree | 61ebb424820644974ca1ab7ef8e3cc34e95dd53a | |
| parent | c56f610fe9470f79c82de3ec765b3c1e66ef2c71 (diff) | |
| download | linux-stable-0a460481df435f955d569b44e7674ff81dfc7f74.tar.gz linux-stable-0a460481df435f955d569b44e7674ff81dfc7f74.tar.bz2 linux-stable-0a460481df435f955d569b44e7674ff81dfc7f74.zip | |
cxl/hdm: Fix a benign lockdep splat
commit 36a1c2ee50f573972aea3c3019555f47ee0094c0 upstream.
The new helper "cxl_num_decoders_committed()" added a lockdep assertion
to validate that port->commit_end is protected against modification.
That assertion fires in init_hdm_decoder() where it is initializing
port->commit_end. Given that it is both accessing and writing that
property it obstensibly needs the lock.
In practice, CXL decoder commit rules (must commit in order) and the
in-order discovery of device decoders makes the manipulation of
->commit_end in init_hdm_decoder() safe. However, rather than rely on
the subtle rules of CXL hardware, just make the implementation obviously
correct from a software perspective.
The Fixes: tag is only for cleaning up a lockdep splat, there is no
functional issue addressed by this fix.
Fixes: 458ba8189cb4 ("cxl: Add cxl_decoders_committed() helper")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/170025232811.2147250.16376901801315194121.stgit@djiang5-mobl3
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/cxl/core/hdm.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c index 54a535f6736b..90664659d5fa 100644 --- a/drivers/cxl/core/hdm.c +++ b/drivers/cxl/core/hdm.c @@ -848,6 +848,8 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld, cxld->target_type = CXL_DECODER_HOSTONLYMEM; else cxld->target_type = CXL_DECODER_DEVMEM; + + guard(rwsem_write)(&cxl_region_rwsem); if (cxld->id != cxl_num_decoders_committed(port)) { dev_warn(&port->dev, "decoder%d.%d: Committed out of order\n", |