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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d1e4f1a99sm52293050f8f.32.2026.04.07.04.27.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Apr 2026 04:27:32 -0700 (PDT) Date: Tue, 7 Apr 2026 13:27:29 +0200 From: Petr Mladek To: Steven Rostedt Cc: Tamir Duberstein , Andy Shevchenko , Rasmus Villemoes , Sergey Senozhatsky , linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel test robot Subject: Re: [PATCH] printf: mark errptr() noinline Message-ID: References: <20260405-printf-test-old-gcc-v1-1-76d24d9bb60e@kernel.org> <20260406111531.779571d7@gandalf.local.home> <20260406123232.3dacbe94@gandalf.local.home> 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: <20260406123232.3dacbe94@gandalf.local.home> On Mon 2026-04-06 12:32:32, Steven Rostedt wrote: > On Mon, 6 Apr 2026 11:21:39 -0400 > Tamir Duberstein wrote: > > > Thanks Steve. IMO that is a very big hammer and not warranted in this > > case. There's been talk of encouraging distros to enable CONFIG_KUNIT > > by default [0], which would probably interact poorly with the change > > you propose. > > > > Branch profiling is really just a niche that is enabled specifically for > seeing all branches taken in the kernel. It hooks to all "if" statements! > As you can imagine, it causes a rather large overhead in performance. > > This option is only used by developers doing special analysis of their code > (namely me ;-). > > The only real concern I would have is if the kunit test developers would > want to use the branch profiling on their code, in which case my suggestion > would prevent that. I wonder if it might be possible to disable the branch profiling just for the printf_kunit.c as a compromise. Would "#undef if" in printf_kunit.c help? Or I see that DISABLE_BRANCH_PROFILING is an official way to disable the feature. I wonder if the following change would solve the problem. I am sorry, I could not test it easily. diff --git a/lib/tests/Makefile b/lib/tests/Makefile index 05f74edbc62b..45d69769ccdf 100644 --- a/lib/tests/Makefile +++ b/lib/tests/Makefile @@ -41,6 +41,7 @@ obj-$(CONFIG_MIN_HEAP_KUNIT_TEST) += min_heap_kunit.o CFLAGS_overflow_kunit.o = $(call cc-disable-warning, tautological-constant-out-of-range-compare) obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o obj-$(CONFIG_PRINTF_KUNIT_TEST) += printf_kunit.o +CFLAGS_printf_kunit.o += -DDISABLE_BRANCH_PROFILING obj-$(CONFIG_RANDSTRUCT_KUNIT_TEST) += randstruct_kunit.o obj-$(CONFIG_SCANF_KUNIT_TEST) += scanf_kunit.o obj-$(CONFIG_SEQ_BUF_KUNIT_TEST) += seq_buf_kunit.o Best Regards, Petr