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[35.130.123.74]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-662fdaf7d0fsm1476337d50.6.2026.06.19.08.19.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jun 2026 08:19:26 -0700 (PDT) From: Yury Norov X-Google-Original-From: Yury Norov Date: Fri, 19 Jun 2026 11:19:25 -0400 To: Linus Torvalds Cc: Steven Rostedt , LKML , Masami Hiramatsu , Mathieu Desnoyers , Ao Sun , David Carlier , Karl Mehltretter , Martin Kaiser , Pengpeng Hou , Qian-Yu Lin , Rik van Riel , Rosen Penev , Shuvam Pandey , Vineeth Pillai , Yash Suthar , Yu Peng Subject: Re: [GIT PULL] tracing: Updates for 7.2 Message-ID: References: <20260616180122.57a3b426@fedora> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jun 18, 2026 at 09:23:04PM -0700, Linus Torvalds wrote: > On Tue, 16 Jun 2026 at 15:01, Steven Rostedt wrote: > > > > tracing: Updates for v7.2: > > I wondered why the heck this causes the whole kernel to be rebuilt, > when the diffstat looked fairly innocuous. > > It's because it changed , which used to be part > of but was split out in commit bec261fec6d4 > ("tracing: move tracing declarations from kernel.h to a dedicated > header"). > > But the second stage of splitting it out - not including it from > - was never done, so now while the diffstat *looks* > innocuous, it is still as deadly to the build as an actual > change would be. > > The intent was clearly to make people who actually needed the > trace_printk() functionality to include the header - that's what the > commit log says. But that's not how any of it works ;( > > So all that commit did was to make things look like they wouldn't hurt > as much as they do, and that trivial change to that file causes a full > rebuild of the kernel. > > I'm not seeing any patches even being discussed that would make only > files that need it to include that file and remove it from > linux/kernel.h that *everybody* uses. Yet that was the *only* point of > making it a separate header in the first place. Yury? Yes, you are right. The original intention was to decouple trace_printk() and kernel.h, and I have the patch for it in v4: https://lore.kernel.org/all/aVvoe5fQN3EUtEAJ@yury/ The Steven's point is the convenience for developers to throw trace_printk() here and there without including any headers. I'm not one of those trace_printk() users, but I take that. Even though, I don't think it's a strong argument, pretty much for the same reasons that you've described above. I suggested adding a debugging flag, so that trace_printk() would be included in kernel.h conditionally, if it's absolutely necessary to have the API included "automatically": > > make D=1 // trace_printk() is available > > make D=0 // trace_printk() is not available > > make // trace_printk() is not available That was rejected too. I even measured 1.5-2% compile time decrease back then. Surely need to retest it to make sure. I'm still for decoupling trace_printk() and kernel.h, so I can resend if needed. Thanks, Yury