From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Poimboeuf Date: Fri, 03 Feb 2023 22:05:09 +0000 Subject: [PATCH 00/22] cpu,sched: Mark arch_cpu_idle_dead() __noreturn Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org Cc: jgross@suse.com, richard.henderson@linaro.org, ink@jurassic.park.msu.ru, mattst88@gmail.com, linux-alpha@vger.kernel.org, linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, linux-csky@vger.kernel.org, linux-ia64@vger.kernel.org, chenhuacai@kernel.org, kernel@xen0n.name, loongarch@lists.linux.dev, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, tsbogend@alpha.franken.de, linux-mips@vger.kernel.org, jiaxun.yang@flygoat.com, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, linuxppc-dev@lists.ozlabs.org, ysato@users.sourceforge.jp, dalias@libc.org, linux-sh@vger.kernel.org, davem@davemloft.net, sparclinux@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, linux-xtensa@linux-xtensa.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org These are some minor changes to enable the __noreturn attribute for arch_cpu_idle_dead(). (If there are no objections, I can merge the entire set through the tip tree.) Until recently [1], in Xen, when a previously offlined CPU was brought back online, it unexpectedly resumed execution where it left off in the middle of the idle loop by returning from play_dead() and its caller arch_cpu_idle_dead(). There were some clever hacks to make that work, but the behavior was surprising as do_idle() doesn't expect an offlined CPU to return from the dead in the middle of the function. Now that Xen has been fixed, make sure arch_cpu_idle_dead() never returns by marking it __noreturn. This causes the compiler to complain if an arch-specific implementation might return. It also improves code generation for both caller and callee. Patches 1-20 update the arch-specific implementations of the function so they don't actually return (even in error cases), and make that visible to the compiler. That's typically done by ending the function with a call to another noreturn function, or with a BUG(). Patch 21 fixes the weak implementation. Patch 22 actually adds the __noreturn attribute. [1] 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead() return") Josh Poimboeuf (22): alpha/cpu: Expose arch_cpu_idle_dead()'s prototype declaration alpha/cpu: Make sure arch_cpu_idle_dead() doesn't return arm/cpu: Make sure arch_cpu_idle_dead() doesn't return arm64/cpu: Mark cpu_die() __noreturn csky/cpu: Make sure arch_cpu_idle_dead() doesn't return ia64/cpu: Mark play_dead() __noreturn loongarch/cpu: Make sure play_dead() doesn't return loongarch/cpu: Mark play_dead() __noreturn mips/cpu: Expose play_dead()'s prototype definition mips/cpu: Make sure play_dead() doesn't return mips/cpu: Mark play_dead() __noreturn powerpc/cpu: Mark start_secondary_resume() __noreturn sh/cpu: Make sure play_dead() doesn't return sh/cpu: Mark play_dead() __noreturn sh/cpu: Expose arch_cpu_idle_dead()'s prototype definition sparc/cpu: Mark cpu_play_dead() __noreturn x86/cpu: Make sure play_dead() doesn't return x86/cpu: Mark play_dead() __noreturn xtensa/cpu: Make sure cpu_die() doesn't return xtensa/cpu: Mark cpu_die() __noreturn sched/idle: Make sure weak version of arch_cpu_idle_dead() doesn't return sched/idle: Mark arch_cpu_idle_dead() __noreturn arch/alpha/kernel/process.c | 2 ++ arch/arm/kernel/smp.c | 2 ++ arch/arm64/include/asm/smp.h | 2 +- arch/csky/kernel/smp.c | 2 ++ arch/ia64/kernel/process.c | 4 ++-- arch/loongarch/include/asm/smp.h | 2 +- arch/loongarch/kernel/smp.c | 2 +- arch/mips/include/asm/smp.h | 2 +- arch/mips/kernel/smp-bmips.c | 3 +++ arch/mips/loongson64/smp.c | 1 + arch/powerpc/include/asm/smp.h | 2 +- arch/sh/include/asm/smp-ops.h | 5 +++-- arch/sh/kernel/idle.c | 1 + arch/sparc/include/asm/smp_64.h | 2 +- arch/x86/include/asm/smp.h | 3 ++- arch/x86/kernel/process.c | 2 +- arch/xtensa/include/asm/smp.h | 2 +- arch/xtensa/kernel/smp.c | 2 ++ include/linux/cpu.h | 2 +- kernel/sched/idle.c | 2 +- tools/objtool/check.c | 1 + 21 files changed, 31 insertions(+), 15 deletions(-) -- 2.39.0