From: Valentin Schneider <valentin.schneider@arm.com> To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rt-users@vger.kernel.org, x86@kernel.org Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Steven Rostedt <rostedt@goodmis.org>, Daniel Bristot de Oliveira <bristot@redhat.com>, "Peter Zijlstra (Intel)" <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Mark Brown <broonie@kernel.org>, Dave Martin <Dave.Martin@arm.com>, Ard Biesheuvel <ardb@kernel.org> Subject: [PATCH 1/3] sched/preempt: Introduce preempt_{enable, disable}_bh() Date: Thu, 22 Jul 2021 18:51:55 +0100 [thread overview] Message-ID: <20210722175157.1367122-2-valentin.schneider@arm.com> (raw) In-Reply-To: <20210722175157.1367122-1-valentin.schneider@arm.com> As pointed out by commit: cba08c5dc6dc ("x86/fpu: Make kernel FPU protection RT friendly") local_bh_disable() is not sufficient under CONFIG_PREEMPT_RT for FPU manipulation. This also affects at least arm64, so package the preemption / softirq enablement handling into a pair of helpers. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- include/linux/bottom_half.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h index eed86eb0a1de..dd98d8c1eb0a 100644 --- a/include/linux/bottom_half.h +++ b/include/linux/bottom_half.h @@ -19,6 +19,24 @@ static inline void local_bh_disable(void) __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); } +/* + * local_bh_disable() protects against both preemption and soft interrupts + * on !RT kernels. + * + * On RT kernels local_bh_disable() is not sufficient because it only + * serializes soft interrupt related sections via a local lock, but stays + * preemptible. Disabling preemption is the right choice here as bottom + * half processing is always in thread context on RT kernels so it + * implicitly prevents bottom half processing as well. + */ +static inline void preempt_disable_bh(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_disable(); + else + local_bh_disable(); +} + extern void _local_bh_enable(void); extern void __local_bh_enable_ip(unsigned long ip, unsigned int cnt); @@ -32,6 +50,14 @@ static inline void local_bh_enable(void) __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); } +static inline void preempt_enable_bh(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_enable(); + else + local_bh_enable(); +} + #ifdef CONFIG_PREEMPT_RT extern bool local_bh_blocked(void); #else -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <valentin.schneider@arm.com> To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rt-users@vger.kernel.org, x86@kernel.org Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Steven Rostedt <rostedt@goodmis.org>, Daniel Bristot de Oliveira <bristot@redhat.com>, "Peter Zijlstra (Intel)" <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Mark Brown <broonie@kernel.org>, Dave Martin <Dave.Martin@arm.com>, Ard Biesheuvel <ardb@kernel.org> Subject: [PATCH 1/3] sched/preempt: Introduce preempt_{enable, disable}_bh() Date: Thu, 22 Jul 2021 18:51:55 +0100 [thread overview] Message-ID: <20210722175157.1367122-2-valentin.schneider@arm.com> (raw) In-Reply-To: <20210722175157.1367122-1-valentin.schneider@arm.com> As pointed out by commit: cba08c5dc6dc ("x86/fpu: Make kernel FPU protection RT friendly") local_bh_disable() is not sufficient under CONFIG_PREEMPT_RT for FPU manipulation. This also affects at least arm64, so package the preemption / softirq enablement handling into a pair of helpers. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- include/linux/bottom_half.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h index eed86eb0a1de..dd98d8c1eb0a 100644 --- a/include/linux/bottom_half.h +++ b/include/linux/bottom_half.h @@ -19,6 +19,24 @@ static inline void local_bh_disable(void) __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); } +/* + * local_bh_disable() protects against both preemption and soft interrupts + * on !RT kernels. + * + * On RT kernels local_bh_disable() is not sufficient because it only + * serializes soft interrupt related sections via a local lock, but stays + * preemptible. Disabling preemption is the right choice here as bottom + * half processing is always in thread context on RT kernels so it + * implicitly prevents bottom half processing as well. + */ +static inline void preempt_disable_bh(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_disable(); + else + local_bh_disable(); +} + extern void _local_bh_enable(void); extern void __local_bh_enable_ip(unsigned long ip, unsigned int cnt); @@ -32,6 +50,14 @@ static inline void local_bh_enable(void) __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET); } +static inline void preempt_enable_bh(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_enable(); + else + local_bh_enable(); +} + #ifdef CONFIG_PREEMPT_RT extern bool local_bh_blocked(void); #else -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-07-22 17:53 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-22 17:51 [PATCH 0/3] sched, x86, arm64: PREEMPT_RT, FPU and preemption Valentin Schneider 2021-07-22 17:51 ` Valentin Schneider 2021-07-22 17:51 ` Valentin Schneider [this message] 2021-07-22 17:51 ` [PATCH 1/3] sched/preempt: Introduce preempt_{enable, disable}_bh() Valentin Schneider 2021-07-22 17:51 ` [PATCH 2/3] x86/fpu: Make FPU protection reuse common helper Valentin Schneider 2021-07-22 17:51 ` Valentin Schneider 2021-07-22 17:51 ` [PATCH 3/3] arm64/fpsimd: Fix FPSIMD context handling vs PREEMPT_RT Valentin Schneider 2021-07-22 17:51 ` Valentin Schneider 2021-07-22 18:32 ` Mark Brown 2021-07-22 18:32 ` Mark Brown 2021-07-23 11:07 ` Valentin Schneider 2021-07-23 11:07 ` Valentin Schneider 2021-07-22 20:11 ` [PATCH 0/3] sched, x86, arm64: PREEMPT_RT, FPU and preemption Andrew Halaney 2021-07-22 20:11 ` Andrew Halaney 2021-07-23 14:12 ` Ard Biesheuvel 2021-07-23 14:12 ` Ard Biesheuvel
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