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Fri, 24 Apr 2026 07:56:27 +0000 Message-ID: Date: Fri, 24 Apr 2026 09:56:16 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V13 2/7] dma-resv: Fix undefined symbol when CONFIG_DMA_SHARED_BUFFER is disabled To: "Mukesh Kumar Chaurasiya (IBM)" , maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com, aliceryhl@google.com, rostedt@goodmis.org, ardb@kernel.org, sumit.semwal@linaro.org, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu, dakr@kernel.org, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, morbo@google.com, justinstitt@google.com, tamird@kernel.org, arnd@arndb.de, nsc@kernel.org, simona.vetter@ffwll.ch, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev References: <20260424054742.45832-1-mkchauras@gmail.com> <20260424054742.45832-3-mkchauras@gmail.com> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20260424054742.45832-3-mkchauras@gmail.com> Content-Type: text/plain; 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CONFIG_DEBUG_MUTEXES=y is enabled > 2. CONFIG_DMA_SHARED_BUFFER is not enabled > 3. dma_resv_reset_max_fences() is declared in the header when > CONFIG_DEBUG_MUTEXES is set > 4. But the function is only compiled in drivers/dma-buf/dma-resv.c, > which is only built when CONFIG_DMA_SHARED_BUFFER is enabled > 5. Rust helpers call dma_resv_unlock() which calls > dma_resv_reset_max_fences(), causing an undefined symbol > > Fix this by making the function declaration conditional on both > CONFIG_DEBUG_MUTEXES and CONFIG_DMA_SHARED_BUFFER. When either is > disabled, use a static inline stub instead. Well we are clearly missing something here, but of hand that doesn't looks like the right fix. When CONFIG_DMA_SHARED_BUFFER isn't enabled then the whole dma-resv.h header can't be used at all. So you also can't call dma_resv_unlock() from the Rust helpers. Which means that we need to make the Rust helpers somehow depend on CONFIG_DMA_SHARED_BUFFER. Alternative would be to provide dummies for the functions in dma-resv.h when CONFIG_DMA_SHARED_BUFFER isn't set, but that looks a bit like it just hides the issue. Regards, Christian. > > Fixes: 0c6b522abc2a ("dma-buf: cleanup dma-resv shared fence debugging a bit v2") > Signed-off-by: Mukesh Kumar Chaurasiya (IBM) > --- > include/linux/dma-resv.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h > index c5ab6fd9ebe8..23c8db0b5214 100644 > --- a/include/linux/dma-resv.h > +++ b/include/linux/dma-resv.h > @@ -311,7 +311,7 @@ static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) > #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) > #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) > > -#ifdef CONFIG_DEBUG_MUTEXES > +#if IS_ENABLED(CONFIG_DEBUG_MUTEXES) && IS_ENABLED(CONFIG_DMA_SHARED_BUFFER) > void dma_resv_reset_max_fences(struct dma_resv *obj); > #else > static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {} > -- > 2.53.0 >