[{"id":29471,"web_url":"https://patchwork.libcamera.org/comment/29471/","msgid":"","date":"2024-05-09T09:49:41","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":143,"url":"https://patchwork.libcamera.org/api/people/143/","name":"Jacopo Mondi","email":"jacopo.mondi@ideasonboard.com"},"content":"Hi Naush\n\nOn Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> The shared_mem_object may be used to construct complex classes, so\n> remove the standard layout type restriction.\n>\n> Signed-off-by: Naushir Patuck \n\nThis looks fine to me, but maybe better check on why this was\nintroduced in first place.\n\nReviewed-by: Jacopo Mondi \n\nThanks\n j\n\n> ---\n> include/libcamera/internal/shared_mem_object.h | 2 +-\n> 1 file changed, 1 insertion(+), 1 deletion(-)\n>\n> diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> index 9b1d939302a8..c9c0482062bd 100644\n> --- a/include/libcamera/internal/shared_mem_object.h\n> +++ b/include/libcamera/internal/shared_mem_object.h\n> @@ -56,7 +56,7 @@ private:\n> \tSpan mem_;\n> };\n>\n> -template::value>>\n> +template\n> class SharedMemObject : public SharedMem\n> {\n> public:\n> --\n> 2.34.1\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 4FB23BDE6B\n\tfor ;\n\tThu, 9 May 2024 09:49:46 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id DAC5963466;\n\tThu, 9 May 2024 11:49:45 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 495A463461\n\tfor ;\n\tThu, 9 May 2024 11:49:44 +0200 (CEST)","from ideasonboard.com (93-61-96-190.ip145.fastwebnet.it\n\t[93.61.96.190])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id CE906524;\n\tThu, 9 May 2024 11:49:40 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"v6Ut6Ca6\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715248180;\n\tbh=XqNuBu64BAEWuRXQ9kCkUz4ORX5CMaRuKYRI4qmEZKA=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=v6Ut6Ca6IajzzGuwqYagLbvU7f3ro3EOAH2mRv5a68huxTGRkA/ypqNeNyieiCcCw\n\t8iriPJ5kUMO9ULeIY520i/3FToHMjwWGopTz3QCFwjhyhNXPnyx6i/ibNTNaWcE5Fg\n\tn+beEw3N64hXSJ+754rlSQ4adSy5Q1T5OcMpjwUU=","Date":"Thu, 9 May 2024 11:49:41 +0200","From":"Jacopo Mondi ","To":"Naushir Patuck ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","Message-ID":"","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20240508080401.14850-7-naush@raspberrypi.com>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29485,"web_url":"https://patchwork.libcamera.org/comment/29485/","msgid":"<171525328740.1857112.17964003539923628686@ping.linuxembedded.co.uk>","date":"2024-05-09T11:14:47","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Quoting Jacopo Mondi (2024-05-09 10:49:41)\n> Hi Naush\n> \n> On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > The shared_mem_object may be used to construct complex classes, so\n> > remove the standard layout type restriction.\n> >\n> > Signed-off-by: Naushir Patuck \n> \n> This looks fine to me, but maybe better check on why this was\n> introduced in first place.\n> \n> Reviewed-by: Jacopo Mondi \n> \n> Thanks\n> j\n> \n> > ---\n> > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > 1 file changed, 1 insertion(+), 1 deletion(-)\n> >\n> > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > index 9b1d939302a8..c9c0482062bd 100644\n> > --- a/include/libcamera/internal/shared_mem_object.h\n> > +++ b/include/libcamera/internal/shared_mem_object.h\n> > @@ -56,7 +56,7 @@ private:\n> > Span mem_;\n> > };\n> >\n> > -template::value>>\n> > +template\n\nI think I'm fine with this as long as the CI builds succeed, so we're\nabout to find out ;-)\n\n\nReviewed-by: Kieran Bingham \n\n> > class SharedMemObject : public SharedMem\n> > {\n> > public:\n> > --\n> > 2.34.1\n> >","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 4BE6FC3226\n\tfor ;\n\tThu, 9 May 2024 11:14:53 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 821BC63465;\n\tThu, 9 May 2024 13:14:52 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 91BAA63460\n\tfor ;\n\tThu, 9 May 2024 13:14:50 +0200 (CEST)","from pendragon.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 0048B904;\n\tThu, 9 May 2024 13:14:46 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"p+tU1OOe\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715253287;\n\tbh=CQ1F3xS3b+08o22OQkN4M4ynRA+0rlnOmbzl/1K0pJQ=;\n\th=In-Reply-To:References:Subject:From:Cc:To:Date:From;\n\tb=p+tU1OOeBrbeZVF0I4DkpXycdhAEZW7IyrxjseY1DpE2l+0++RntvSErbmc1Psp0Y\n\tx0kT4AkkQVsqy3W+yMRY4d7ZRiJX8C3GIZpCKzUPcijpBZYtoJLguY579pJWHfpKM5\n\t2xTZAtKeKFik4qQnskBCXFA9WdahsYPR8fjMNW6Q=","Content-Type":"text/plain; charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"quoted-printable","In-Reply-To":"","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>\n\t","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","From":"Kieran Bingham ","Cc":"libcamera-devel@lists.libcamera.org","To":"Jacopo Mondi ,\n\tNaushir Patuck ","Date":"Thu, 09 May 2024 12:14:47 +0100","Message-ID":"<171525328740.1857112.17964003539923628686@ping.linuxembedded.co.uk>","User-Agent":"alot/0.10","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29487,"web_url":"https://patchwork.libcamera.org/comment/29487/","msgid":"<20240509111615.GF14520@pendragon.ideasonboard.com>","date":"2024-05-09T11:16:15","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > The shared_mem_object may be used to construct complex classes, so\n> > remove the standard layout type restriction.\n> >\n> > Signed-off-by: Naushir Patuck \n> \n> This looks fine to me, but maybe better check on why this was\n> introduced in first place.\n\nIt was added there because sharing objects containing pointers between\ndifferent processes isn't safe. Naush, what object do you need to store\nin shared memory that has a non-standard layout, but is still safe to\nshare ?\n\n> Reviewed-by: Jacopo Mondi \n> \n> > ---\n> > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > 1 file changed, 1 insertion(+), 1 deletion(-)\n> >\n> > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > index 9b1d939302a8..c9c0482062bd 100644\n> > --- a/include/libcamera/internal/shared_mem_object.h\n> > +++ b/include/libcamera/internal/shared_mem_object.h\n> > @@ -56,7 +56,7 @@ private:\n> > \tSpan mem_;\n> > };\n> >\n> > -template::value>>\n> > +template\n> > class SharedMemObject : public SharedMem\n> > {\n> > public:","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id AD70EC3226\n\tfor ;\n\tThu, 9 May 2024 11:16:25 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 529756346B;\n\tThu, 9 May 2024 13:16:25 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 7128F63460\n\tfor ;\n\tThu, 9 May 2024 13:16:24 +0200 (CEST)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id D76CC904;\n\tThu, 9 May 2024 13:16:20 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"d66ZyoiC\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715253381;\n\tbh=F2n3J6KhVFXOxosN3xrwfQKlKfJv64XC890/e48l+w0=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=d66ZyoiC4Je6tupOmLHkkccPnJmYkUnF7rtHiKv+9vH6zVYyjtjU5jOh/RdmpirBP\n\t+0tDW+xMnMlUj/xLAfTxXl2kwpUbS2G7bM6Atl/P27JXTHXduuzzc5KTZ0dgPCbz7L\n\th1GFXvZaWi8Rf3s4kPl7UPML0+HAn8x8MaBGMpPA=","Date":"Thu, 9 May 2024 14:16:15 +0300","From":"Laurent Pinchart ","To":"Jacopo Mondi ","Cc":"Naushir Patuck ,\n\tlibcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","Message-ID":"<20240509111615.GF14520@pendragon.ideasonboard.com>","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>\n\t","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29489,"web_url":"https://patchwork.libcamera.org/comment/29489/","msgid":"<171525377694.1857112.11429837573698659405@ping.linuxembedded.co.uk>","date":"2024-05-09T11:22:56","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Quoting Laurent Pinchart (2024-05-09 12:16:15)\n> On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > > The shared_mem_object may be used to construct complex classes, so\n> > > remove the standard layout type restriction.\n> > >\n> > > Signed-off-by: Naushir Patuck \n> > \n> > This looks fine to me, but maybe better check on why this was\n> > introduced in first place.\n> \n> It was added there because sharing objects containing pointers between\n> different processes isn't safe. Naush, what object do you need to store\n> in shared memory that has a non-standard layout, but is still safe to\n> share ?\n\nOh, interesting point. I wonder if that's why we've seen people get\nsegfaults if the RPi IPA runs in isolation (as then these buffers are\nshared, and could potentially contain invalid pointers?)\n\n--\nKieran\n\n\n> \n> > Reviewed-by: Jacopo Mondi \n> > \n> > > ---\n> > > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > > 1 file changed, 1 insertion(+), 1 deletion(-)\n> > >\n> > > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > > index 9b1d939302a8..c9c0482062bd 100644\n> > > --- a/include/libcamera/internal/shared_mem_object.h\n> > > +++ b/include/libcamera/internal/shared_mem_object.h\n> > > @@ -56,7 +56,7 @@ private:\n> > > Span mem_;\n> > > };\n> > >\n> > > -template::value>>\n> > > +template\n> > > class SharedMemObject : public SharedMem\n> > > {\n> > > public:\n> \n> -- \n> Regards,\n> \n> Laurent Pinchart","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id B29B4C3226\n\tfor ;\n\tThu, 9 May 2024 11:23:02 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D85B463460;\n\tThu, 9 May 2024 13:23:01 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 37D986342D\n\tfor ;\n\tThu, 9 May 2024 13:23:00 +0200 (CEST)","from pendragon.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 80392904;\n\tThu, 9 May 2024 13:22:56 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"ZQhYfDsr\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715253776;\n\tbh=lfAchs00l4y52Sp68udcn3m6RyZoGrhO/oydIOKjmAE=;\n\th=In-Reply-To:References:Subject:From:Cc:To:Date:From;\n\tb=ZQhYfDsrfyX14d66U5YPLkfFxuc7pf6RfywHitMQtIsFqGWd6DU3wOkKgoCNg4muy\n\tWiOwCT50DydNwmZT27aKfuhu+qrAmnngNQ31U3ID6/RadzUO5daQeTI2mhHpLawkpC\n\tKAc+SCnwN4zARnQpSid+LnO+5FlCVi7vpYAGATA4=","Content-Type":"text/plain; charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"quoted-printable","In-Reply-To":"<20240509111615.GF14520@pendragon.ideasonboard.com>","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>\n\t\n\t<20240509111615.GF14520@pendragon.ideasonboard.com>","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","From":"Kieran Bingham ","Cc":"Naushir Patuck ,\n\tlibcamera-devel@lists.libcamera.org","To":"Jacopo Mondi ,\n\tLaurent Pinchart ","Date":"Thu, 09 May 2024 12:22:56 +0100","Message-ID":"<171525377694.1857112.11429837573698659405@ping.linuxembedded.co.uk>","User-Agent":"alot/0.10","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29491,"web_url":"https://patchwork.libcamera.org/comment/29491/","msgid":"<20240509113124.GI14520@pendragon.ideasonboard.com>","date":"2024-05-09T11:31:24","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Thu, May 09, 2024 at 12:22:56PM +0100, Kieran Bingham wrote:\n> Quoting Laurent Pinchart (2024-05-09 12:16:15)\n> > On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> > > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > > > The shared_mem_object may be used to construct complex classes, so\n> > > > remove the standard layout type restriction.\n> > > >\n> > > > Signed-off-by: Naushir Patuck \n> > > \n> > > This looks fine to me, but maybe better check on why this was\n> > > introduced in first place.\n> > \n> > It was added there because sharing objects containing pointers between\n> > different processes isn't safe. Naush, what object do you need to store\n> > in shared memory that has a non-standard layout, but is still safe to\n> > share ?\n> \n> Oh, interesting point. I wonder if that's why we've seen people get\n> segfaults if the RPi IPA runs in isolation (as then these buffers are\n> shared, and could potentially contain invalid pointers?)\n\nOn Pi4 the only shared buffer I'm aware of contains the LSC table, so\nthat should be fine. I haven't checked Pi5.\n\nThe std::is_standard_layout() check doesn't catch pointers\nunfortunately, but it catches C++ objects that can contain pointers\n(such as containers from the C++ standard library). It may also catch\nobjects that are fine, if that's the case here, we can try to relax the\ncheck.\n\n> > > Reviewed-by: Jacopo Mondi \n> > > \n> > > > ---\n> > > > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > > > 1 file changed, 1 insertion(+), 1 deletion(-)\n> > > >\n> > > > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > > > index 9b1d939302a8..c9c0482062bd 100644\n> > > > --- a/include/libcamera/internal/shared_mem_object.h\n> > > > +++ b/include/libcamera/internal/shared_mem_object.h\n> > > > @@ -56,7 +56,7 @@ private:\n> > > > Span mem_;\n> > > > };\n> > > >\n> > > > -template::value>>\n> > > > +template\n> > > > class SharedMemObject : public SharedMem\n> > > > {\n> > > > public:","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id BC71AC3226\n\tfor ;\n\tThu, 9 May 2024 11:31:36 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id EB0E463433;\n\tThu, 9 May 2024 13:31:35 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 00F926342D\n\tfor ;\n\tThu, 9 May 2024 13:31:33 +0200 (CEST)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 19D6E904;\n\tThu, 9 May 2024 13:31:30 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"UV+lpcpM\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715254290;\n\tbh=xIFtEbYSKqVmJWKpWZcRjjn02MeL3BE0p57pP8cOVaU=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=UV+lpcpMSyEGQ7Xjm5gCsIvfsJsWjhKgJVguESGt+IlPzwZxZC2sxOL0hZiTvbK08\n\tZ9/DN556YVjU6vgOJMY+zj2g8CN1DJ0jePzJu/OYQZ8Xg8XOxe9yLwc+dCE4mPTBP6\n\tXSscFkYtz7cBRRSdomNRLiDM92rEmS71NIZUJAxU=","Date":"Thu, 9 May 2024 14:31:24 +0300","From":"Laurent Pinchart ","To":"Kieran Bingham ","Cc":"Jacopo Mondi ,\n\tNaushir Patuck ,\n\tlibcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","Message-ID":"<20240509113124.GI14520@pendragon.ideasonboard.com>","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>\n\t\n\t<20240509111615.GF14520@pendragon.ideasonboard.com>\n\t<171525377694.1857112.11429837573698659405@ping.linuxembedded.co.uk>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<171525377694.1857112.11429837573698659405@ping.linuxembedded.co.uk>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29497,"web_url":"https://patchwork.libcamera.org/comment/29497/","msgid":"","date":"2024-05-09T11:55:20","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":34,"url":"https://patchwork.libcamera.org/api/people/34/","name":"Naushir Patuck","email":"naush@raspberrypi.com"},"content":"On Thu, 9 May 2024 at 12:31, Laurent Pinchart <\nlaurent.pinchart@ideasonboard.com> wrote:\n\n> On Thu, May 09, 2024 at 12:22:56PM +0100, Kieran Bingham wrote:\n> > Quoting Laurent Pinchart (2024-05-09 12:16:15)\n> > > On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> > > > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > > > > The shared_mem_object may be used to construct complex classes, so\n> > > > > remove the standard layout type restriction.\n> > > > >\n> > > > > Signed-off-by: Naushir Patuck \n> > > >\n> > > > This looks fine to me, but maybe better check on why this was\n> > > > introduced in first place.\n> > >\n> > > It was added there because sharing objects containing pointers between\n> > > different processes isn't safe. Naush, what object do you need to store\n> > > in shared memory that has a non-standard layout, but is still safe to\n> > > share ?\n> >\n> > Oh, interesting point. I wonder if that's why we've seen people get\n> > segfaults if the RPi IPA runs in isolation (as then these buffers are\n> > shared, and could potentially contain invalid pointers?)\n>\n> On Pi4 the only shared buffer I'm aware of contains the LSC table, so\n> that should be fine. I haven't checked Pi5.\n>\n\nThe Pi 4 LS tables use a dmabuf and FD between the pipeline handler and\nIPA, so that's ok.\n\n>\n> The std::is_standard_layout() check doesn't catch pointers\n> unfortunately, but it catches C++ objects that can contain pointers\n> (such as containers from the C++ standard library). It may also catch\n> objects that are fine, if that's the case here, we can try to relax the\n> check.\n>\n\nEek, this can be nasty. Frontend is safe, but Backend is not. We don't\nuse any pointers but have a couple of std::vectors, these can easily be\nremoved. It does have a few std::map types that are problematic. We only\never access these maps and vectors from the pipeline handler side, so\nit \"works\", but potentially fragile. I don't know what to do here...\n\n\n>\n> > > > Reviewed-by: Jacopo Mondi \n> > > >\n> > > > > ---\n> > > > > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > > > > 1 file changed, 1 insertion(+), 1 deletion(-)\n> > > > >\n> > > > > diff --git a/include/libcamera/internal/shared_mem_object.h\n> b/include/libcamera/internal/shared_mem_object.h\n> > > > > index 9b1d939302a8..c9c0482062bd 100644\n> > > > > --- a/include/libcamera/internal/shared_mem_object.h\n> > > > > +++ b/include/libcamera/internal/shared_mem_object.h\n> > > > > @@ -56,7 +56,7 @@ private:\n> > > > > Span mem_;\n> > > > > };\n> > > > >\n> > > > > -template std::enable_if_t::value>>\n> > > > > +template\n> > > > > class SharedMemObject : public SharedMem\n> > > > > {\n> > > > > public:\n>\n> --\n> Regards,\n>\n> Laurent Pinchart\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 14E5EC3226\n\tfor ;\n\tThu, 9 May 2024 11:55:53 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id E91106345F;\n\tThu, 9 May 2024 13:55:51 +0200 (CEST)","from mail-yw1-x112e.google.com (mail-yw1-x112e.google.com\n\t[IPv6:2607:f8b0:4864:20::112e])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 4D71C633FA\n\tfor ;\n\tThu, 9 May 2024 13:55:50 +0200 (CEST)","by mail-yw1-x112e.google.com with SMTP id\n\t00721157ae682-61be4b98766so8393857b3.3\n\tfor ;\n\tThu, 09 May 2024 04:55:50 -0700 (PDT)"],"Authentication-Results":"lancelot.ideasonboard.com; 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boundary=\"000000000000a0127006180419c7\"","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29498,"web_url":"https://patchwork.libcamera.org/comment/29498/","msgid":"<20240509122603.GA17123@pendragon.ideasonboard.com>","date":"2024-05-09T12:26:03","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Naush,\n\nOn Thu, May 09, 2024 at 12:55:20PM +0100, Naushir Patuck wrote:\n> On Thu, 9 May 2024 at 12:31, Laurent Pinchart wrote:\n> > On Thu, May 09, 2024 at 12:22:56PM +0100, Kieran Bingham wrote:\n> > > Quoting Laurent Pinchart (2024-05-09 12:16:15)\n> > > > On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> > > > > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > > > > > The shared_mem_object may be used to construct complex classes, so\n> > > > > > remove the standard layout type restriction.\n> > > > > >\n> > > > > > Signed-off-by: Naushir Patuck \n> > > > >\n> > > > > This looks fine to me, but maybe better check on why this was\n> > > > > introduced in first place.\n> > > >\n> > > > It was added there because sharing objects containing pointers between\n> > > > different processes isn't safe. Naush, what object do you need to store\n> > > > in shared memory that has a non-standard layout, but is still safe to\n> > > > share ?\n> > >\n> > > Oh, interesting point. I wonder if that's why we've seen people get\n> > > segfaults if the RPi IPA runs in isolation (as then these buffers are\n> > > shared, and could potentially contain invalid pointers?)\n> >\n> > On Pi4 the only shared buffer I'm aware of contains the LSC table, so\n> > that should be fine. I haven't checked Pi5.\n> \n> The Pi 4 LS tables use a dmabuf and FD between the pipeline handler and\n> IPA, so that's ok.\n\nAh yes, I forgot for a moment it was using dmabuf.\n\n> > The std::is_standard_layout() check doesn't catch pointers\n> > unfortunately, but it catches C++ objects that can contain pointers\n> > (such as containers from the C++ standard library). It may also catch\n> > objects that are fine, if that's the case here, we can try to relax the\n> > check.\n> \n> Eek, this can be nasty. Frontend is safe, but Backend is not. We don't\n> use any pointers but have a couple of std::vectors, these can easily be\n> removed. It does have a few std::map types that are problematic. We only\n> ever access these maps and vectors from the pipeline handler side, so\n> it \"works\", but potentially fragile. I don't know what to do here...\n\nCan we discuss this by looking at the problematic code, and the layout\nof the object you want to share between the pipeline handler and IPA\nside ? A short explanation regarding what parts of the data are read and\nwritten on each side will be useful.\n\n> > > > > Reviewed-by: Jacopo Mondi \n> > > > >\n> > > > > > ---\n> > > > > > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > > > > > 1 file changed, 1 insertion(+), 1 deletion(-)\n> > > > > >\n> > > > > > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > > > > > index 9b1d939302a8..c9c0482062bd 100644\n> > > > > > --- a/include/libcamera/internal/shared_mem_object.h\n> > > > > > +++ b/include/libcamera/internal/shared_mem_object.h\n> > > > > > @@ -56,7 +56,7 @@ private:\n> > > > > > Span mem_;\n> > > > > > };\n> > > > > >\n> > > > > > -template::value>>\n> > > > > > +template\n> > > > > > class SharedMemObject : public SharedMem\n> > > > > > {\n> > > > > > public:","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id E9218BDE6B\n\tfor ;\n\tThu, 9 May 2024 12:26:14 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D4B776345F;\n\tThu, 9 May 2024 14:26:13 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 61590633FA\n\tfor ;\n\tThu, 9 May 2024 14:26:12 +0200 (CEST)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 831F9CC8;\n\tThu, 9 May 2024 14:26:08 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"eumHKkFV\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1715257568;\n\tbh=9lktKRN+mVl8jN568yh14plU5x7v4mMZskjQSnTxTos=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=eumHKkFVr05ImkADa20VL/AKTbeK4ciI6ktoU2zI0rhGvOcvLr1aEHVcYRfolW2+V\n\tI2VnbTqzdIPT8H8CX24k86Ug91f4JEM6TKwT7zkuKoPjdxbsY+oZzEXTVf36Tx4hUx\n\tAIw0+5sWQDrRaDpOCQHPX9CfITd8PsOtc+TK0XBk=","Date":"Thu, 9 May 2024 15:26:03 +0300","From":"Laurent Pinchart ","To":"Naushir Patuck ","Cc":"Kieran Bingham ,\n\tJacopo Mondi ,\n\tlibcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","Message-ID":"<20240509122603.GA17123@pendragon.ideasonboard.com>","References":"<20240508080401.14850-1-naush@raspberrypi.com>\n\t<20240508080401.14850-7-naush@raspberrypi.com>\n\t\n\t<20240509111615.GF14520@pendragon.ideasonboard.com>\n\t<171525377694.1857112.11429837573698659405@ping.linuxembedded.co.uk>\n\t<20240509113124.GI14520@pendragon.ideasonboard.com>\n\t","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":29499,"web_url":"https://patchwork.libcamera.org/comment/29499/","msgid":"","date":"2024-05-09T13:38:02","subject":"Re: [PATCH v2 6/6] libcamera: shared_mem_object: Remove\n\tis_standard_layout restriction","submitter":{"id":34,"url":"https://patchwork.libcamera.org/api/people/34/","name":"Naushir Patuck","email":"naush@raspberrypi.com"},"content":"On Thu, 9 May 2024 at 13:26, Laurent Pinchart\n wrote:\n>\n> Hi Naush,\n>\n> On Thu, May 09, 2024 at 12:55:20PM +0100, Naushir Patuck wrote:\n> > On Thu, 9 May 2024 at 12:31, Laurent Pinchart wrote:\n> > > On Thu, May 09, 2024 at 12:22:56PM +0100, Kieran Bingham wrote:\n> > > > Quoting Laurent Pinchart (2024-05-09 12:16:15)\n> > > > > On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:\n> > > > > > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:\n> > > > > > > The shared_mem_object may be used to construct complex classes, so\n> > > > > > > remove the standard layout type restriction.\n> > > > > > >\n> > > > > > > Signed-off-by: Naushir Patuck \n> > > > > >\n> > > > > > This looks fine to me, but maybe better check on why this was\n> > > > > > introduced in first place.\n> > > > >\n> > > > > It was added there because sharing objects containing pointers between\n> > > > > different processes isn't safe. Naush, what object do you need to store\n> > > > > in shared memory that has a non-standard layout, but is still safe to\n> > > > > share ?\n> > > >\n> > > > Oh, interesting point. I wonder if that's why we've seen people get\n> > > > segfaults if the RPi IPA runs in isolation (as then these buffers are\n> > > > shared, and could potentially contain invalid pointers?)\n> > >\n> > > On Pi4 the only shared buffer I'm aware of contains the LSC table, so\n> > > that should be fine. I haven't checked Pi5.\n> >\n> > The Pi 4 LS tables use a dmabuf and FD between the pipeline handler and\n> > IPA, so that's ok.\n>\n> Ah yes, I forgot for a moment it was using dmabuf.\n>\n> > > The std::is_standard_layout() check doesn't catch pointers\n> > > unfortunately, but it catches C++ objects that can contain pointers\n> > > (such as containers from the C++ standard library). It may also catch\n> > > objects that are fine, if that's the case here, we can try to relax the\n> > > check.\n> >\n> > Eek, this can be nasty. Frontend is safe, but Backend is not. We don't\n> > use any pointers but have a couple of std::vectors, these can easily be\n> > removed. It does have a few std::map types that are problematic. We only\n> > ever access these maps and vectors from the pipeline handler side, so\n> > it \"works\", but potentially fragile. I don't know what to do here...\n>\n> Can we discuss this by looking at the problematic code, and the layout\n> of the object you want to share between the pipeline handler and IPA\n> side ? A short explanation regarding what parts of the data are read and\n> written on each side will be useful.\n\n\nOk, this turned out to be a lot less painful than I expected. I've\nmanaged to make classes FrontEnd and BackEnd standard layout types by\ngetting rid of a const reference and the std::maps.\n\nWe can remove this patch from the series. I'll post an update to\nlibpisp with the changes shortly for you to have a look at the needed\nchanges.\n\nNaush\n\n>\n> > > > > > Reviewed-by: Jacopo Mondi \n> > > > > >\n> > > > > > > ---\n> > > > > > > include/libcamera/internal/shared_mem_object.h | 2 +-\n> > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-)\n> > > > > > >\n> > > > > > > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h\n> > > > > > > index 9b1d939302a8..c9c0482062bd 100644\n> > > > > > > --- a/include/libcamera/internal/shared_mem_object.h\n> > > > > > > +++ b/include/libcamera/internal/shared_mem_object.h\n> > > > > > > @@ -56,7 +56,7 @@ private:\n> > > > > > > Span mem_;\n> > > > > > > };\n> > > > > > >\n> > > > > > > -template::value>>\n> > > > > > > +template\n> > > > > > > class SharedMemObject : public SharedMem\n> > > > > > > {\n> > > > > > > public:\n>\n> --\n> Regards,\n>\n> Laurent Pinchart","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 2E3AAC3226\n\tfor ;\n\tThu, 9 May 2024 13:38:42 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 331096345F;\n\tThu, 9 May 2024 15:38:41 +0200 (CEST)","from mail-yb1-xb35.google.com (mail-yb1-xb35.google.com\n\t[IPv6:2607:f8b0:4864:20::b35])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 4E06C633FA\n\tfor ;\n\tThu, 9 May 2024 15:38:39 +0200 (CEST)","by mail-yb1-xb35.google.com with SMTP id\n\t3f1490d57ef6-de45dba157cso795889276.3\n\tfor ;\n\tThu, 09 May 2024 06:38:39 -0700 (PDT)"],"Authentication-Results":"lancelot.ideasonboard.com; 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