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[209.132.180.67]) by mx.google.com with ESMTP id 97-v6si2905658pld.345.2018.06.26.19.27.15; Tue, 26 Jun 2018 19:27:30 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752178AbeF0AnV (ORCPT + 99 others); Tue, 26 Jun 2018 20:43:21 -0400 Received: from gateway36.websitewelcome.com ([192.185.185.36]:26755 "EHLO gateway36.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751409AbeF0AnT (ORCPT ); Tue, 26 Jun 2018 20:43:19 -0400 Received: from cm12.websitewelcome.com (cm12.websitewelcome.com [100.42.49.8]) by gateway36.websitewelcome.com (Postfix) with ESMTP id BFECD40103E9D for ; Tue, 26 Jun 2018 18:43:38 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id XyYIfp9YNSjJAXyYIfLPyH; Tue, 26 Jun 2018 19:43:18 -0500 X-Authority-Reason: nr=8 Received: from [189.250.65.56] (port=54870 helo=[192.168.1.71]) by gator4166.hostgator.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.91) (envelope-from ) id 1fXyYI-000ly1-D6; Tue, 26 Jun 2018 19:43:18 -0500 Subject: Re: [Intel-gfx] [PATCH] drm/i915: mark expected switch fall-through To: Jani Nikula , Rodrigo Vivi Cc: Joonas Lahtinen , David Airlie , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20180620133100.GA608@embeddedor.com> <20180620190628.GC8258@intel.com> <26740470-d7b7-0a58-0aae-fc628bd4f416@embeddedor.com> <87r2l0va65.fsf@intel.com> From: "Gustavo A. R. Silva" Openpgp: preference=signencrypt Autocrypt: addr=gustavo@embeddedor.com; keydata= xsFNBFssHAwBEADIy3ZoPq3z5UpsUknd2v+IQud4TMJnJLTeXgTf4biSDSrXn73JQgsISBwG 2Pm4wnOyEgYUyJd5tRWcIbsURAgei918mck3tugT7AQiTUN3/5aAzqe/4ApDUC+uWNkpNnSV tjOx1hBpla0ifywy4bvFobwSh5/I3qohxDx+c1obd8Bp/B/iaOtnq0inli/8rlvKO9hp6Z4e DXL3PlD0QsLSc27AkwzLEc/D3ZaqBq7ItvT9Pyg0z3Q+2dtLF00f9+663HVC2EUgP25J3xDd 496SIeYDTkEgbJ7WYR0HYm9uirSET3lDqOVh1xPqoy+U9zTtuA9NQHVGk+hPcoazSqEtLGBk YE2mm2wzX5q2uoyptseSNceJ+HE9L+z1KlWW63HhddgtRGhbP8pj42bKaUSrrfDUsicfeJf6 m1iJRu0SXYVlMruGUB1PvZQ3O7TsVfAGCv85pFipdgk8KQnlRFkYhUjLft0u7CL1rDGZWDDr NaNj54q2CX9zuSxBn9XDXvGKyzKEZ4NY1Jfw+TAMPCp4buawuOsjONi2X0DfivFY+ZsjAIcx qQMglPtKk/wBs7q2lvJ+pHpgvLhLZyGqzAvKM1sVtRJ5j+ARKA0w4pYs5a5ufqcfT7dN6TBk LXZeD9xlVic93Ju08JSUx2ozlcfxq+BVNyA+dtv7elXUZ2DrYwARAQABzSxHdXN0YXZvIEEu IFIuIFNpbHZhIDxndXN0YXZvQGVtYmVkZGVkb3IuY29tPsLBfQQTAQgAJwUCWywcDAIbIwUJ CWYBgAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRBHBbTLRwbbMZ6tEACk0hmmZ2FWL1Xi l/bPqDGFhzzexrdkXSfTTZjBV3a+4hIOe+jl6Rci/CvRicNW4H9yJHKBrqwwWm9fvKqOBAg9 obq753jydVmLwlXO7xjcfyfcMWyx9QdYLERTeQfDAfRqxir3xMeOiZwgQ6dzX3JjOXs6jHBP cgry90aWbaMpQRRhaAKeAS14EEe9TSIly5JepaHoVdASuxklvOC0VB0OwNblVSR2S5i5hSsh ewbOJtwSlonsYEj4EW1noQNSxnN/vKuvUNegMe+LTtnbbocFQ7dGMsT3kbYNIyIsp42B5eCu JXnyKLih7rSGBtPgJ540CjoPBkw2mCfhj2p5fElRJn1tcX2McsjzLFY5jK9RYFDavez5w3lx JFgFkla6sQHcrxH62gTkb9sUtNfXKucAfjjCMJ0iuQIHRbMYCa9v2YEymc0k0RvYr43GkA3N PJYd/vf9vU7VtZXaY4a/dz1d9dwIpyQARFQpSyvt++R74S78eY/+lX8wEznQdmRQ27kq7BJS R20KI/8knhUNUJR3epJu2YFT/JwHbRYC4BoIqWl+uNvDf+lUlI/D1wP+lCBSGr2LTkQRoU8U 64iK28BmjJh2K3WHmInC1hbUucWT7Swz/+6+FCuHzap/cjuzRN04Z3Fdj084oeUNpP6+b9yW e5YnLxF8ctRAp7K4yVlvA87BTQRbLBwMARAAsHCE31Ffrm6uig1BQplxMV8WnRBiZqbbsVJB H1AAh8tq2ULl7udfQo1bsPLGGQboJSVN9rckQQNahvHAIK8ZGfU4Qj8+CER+fYPp/MDZj+t0 DbnWSOrG7z9HIZo6PR9z4JZza3Hn/35jFggaqBtuydHwwBANZ7A6DVY+W0COEU4of7CAahQo 5NwYiwS0lGisLTqks5R0Vh+QpvDVfuaF6I8LUgQR/cSgLkR//V1uCEQYzhsoiJ3zc1HSRyOP otJTApqGBq80X0aCVj1LOiOF4rrdvQnj6iIlXQssdb+WhSYHeuJj1wD0ZlC7ds5zovXh+FfF l5qH5RFY/qVn3mNIVxeO987WSF0jh+T5ZlvUNdhedGndRmwFTxq2Li6GNMaolgnpO/CPcFpD jKxY/HBUSmaE9rNdAa1fCd4RsKLlhXda+IWpJZMHlmIKY8dlUybP+2qDzP2lY7kdFgPZRU+e zS/pzC/YTzAvCWM3tDgwoSl17vnZCr8wn2/1rKkcLvTDgiJLPCevqpTb6KFtZosQ02EGMuHQ I6Zk91jbx96nrdsSdBLGH3hbvLvjZm3C+fNlVb9uvWbdznObqcJxSH3SGOZ7kCHuVmXUcqoz ol6ioMHMb+InrHPP16aVDTBTPEGwgxXI38f7SUEn+NpbizWdLNz2hc907DvoPm6HEGCanpcA EQEAAcLBZQQYAQgADwUCWywcDAIbDAUJCWYBgAAKCRBHBbTLRwbbMdsZEACUjmsJx2CAY+QS UMebQRFjKavwXB/xE7fTt2ahuhHT8qQ/lWuRQedg4baInw9nhoPE+VenOzhGeGlsJ0Ys52sd XvUjUocKgUQq6ekOHbcw919nO5L9J2ejMf/VC/quN3r3xijgRtmuuwZjmmi8ct24TpGeoBK4 WrZGh/1hAYw4ieARvKvgjXRstcEqM5thUNkOOIheud/VpY+48QcccPKbngy//zNJWKbRbeVn imua0OpqRXhCrEVm/xomeOvl1WK1BVO7z8DjSdEBGzbV76sPDJb/fw+y+VWrkEiddD/9CSfg fBNOb1p1jVnT2mFgGneIWbU0zdDGhleI9UoQTr0e0b/7TU+Jo6TqwosP9nbk5hXw6uR5k5PF 8ieyHVq3qatJ9K1jPkBr8YWtI5uNwJJjTKIA1jHlj8McROroxMdI6qZ/wZ1ImuylpJuJwCDC ORYf5kW61fcrHEDlIvGc371OOvw6ejF8ksX5+L2zwh43l/pKkSVGFpxtMV6d6J3eqwTafL86 YJWH93PN+ZUh6i6Rd2U/i8jH5WvzR57UeWxE4P8bQc0hNGrUsHQH6bpHV2lbuhDdqo+cM9eh GZEO3+gCDFmKrjspZjkJbB5Gadzvts5fcWGOXEvuT8uQSvl+vEL0g6vczsyPBtqoBLa9SNrS VtSixD1uOgytAP7RWS474w== Message-ID: <357b53aa-d8ce-c9db-0b81-2e8e1aa821bb@embeddedor.com> Date: Tue, 26 Jun 2018 19:43:16 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <87r2l0va65.fsf@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.250.65.56 X-Source-L: No X-Exim-ID: 1fXyYI-000ly1-D6 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.71]) [189.250.65.56]:54870 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 11 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jani, On 06/21/2018 03:03 AM, Jani Nikula wrote: > On Wed, 20 Jun 2018, "Gustavo A. R. Silva" wrote: >> On 06/20/2018 02:06 PM, Rodrigo Vivi wrote: >>> On Wed, Jun 20, 2018 at 08:31:00AM -0500, Gustavo A. R. Silva wrote: >>>> In preparation to enabling -Wimplicit-fallthrough, mark switch cases >>>> where we are expecting to fall through. >>>> >>>> Addresses-Coverity-ID: 1470102 ("Missing break in switch") >>> >>> Any other advantage besides coverity? >>> Can't we address it by marking as "Intentional" on the tool? >>> >> >> Yes. The advantage of this is that it will eventually allows to enable >> -Wimplicit-fallthrough, hence, enabling the compiler to trigger a >> warning, which will force us to double check if we are actually missing >> a break before committing the code. > > I applaud the efforts. Since you're doing the comment changes, do you > have an idea what -Wimplicit-fallthrough=N level is being considered for > kernel? > Currently, we are trying level 2. >>> I'm afraid there will be so many more places to add fallthrough >>> marks.... >>> >> >> Oh yeah, there are around 1000 similar places in the whole codebase. >> There is an ongoing effort to review each case. Months ago, it used to >> be around 1500 of these cases. > > We use our own MISSING_CASE() to indicate stuff that's not supposed to > happen, or to be implemented, etc. and in many cases the fallthrough is > normal. I wonder if we could embed __attribute__ ((fallthrough)) in > there to tackle all of these without a comment. > I've tried this: diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h index 00165ad..829572c 100644 --- a/drivers/gpu/drm/i915/i915_utils.h +++ b/drivers/gpu/drm/i915/i915_utils.h @@ -40,8 +40,10 @@ #undef WARN_ON_ONCE #define WARN_ON_ONCE(x) WARN_ONCE((x), "%s", "WARN_ON_ONCE(" __stringify(x) ")") -#define MISSING_CASE(x) WARN(1, "Missing case (%s == %ld)\n", \ - __stringify(x), (long)(x)) +#define MISSING_CASE(x) ({ \ + WARN(1, "Missing case (%s == %ld)\n", __stringify(x), (long)(x)); \ + __attribute__ ((fallthrough)); \ +}) #if GCC_VERSION >= 70000 #define add_overflows(A, B) \ and I get the following warnings as a consequence: drivers/gpu/drm/i915/intel_pm.c: In function ‘intel_init_clock_gating_hooks’: drivers/gpu/drm/i915/i915_utils.h:48:2: error: invalid use of attribute ‘fallthrough’ __attribute__ ((fallthrough)); \ ^ drivers/gpu/drm/i915/intel_pm.c:9240:3: note: in expansion of macro ‘MISSING_CASE’ MISSING_CASE(INTEL_DEVID(dev_priv)); ^~~~~~~~~~~~ drivers/gpu/drm/i915/intel_pm.c: In function ‘intel_read_wm_latency’: drivers/gpu/drm/i915/i915_utils.h:48:2: error: invalid use of attribute ‘fallthrough’ __attribute__ ((fallthrough)); \ ^ drivers/gpu/drm/i915/intel_pm.c:2902:3: note: in expansion of macro ‘MISSING_CASE’ MISSING_CASE(INTEL_DEVID(dev_priv)); ^~~~~~~~~~~~ Thanks -- Gustavo