From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH RT 08/10] x86/preempt-lazy: fixup should_resched() Date: Thu, 22 Sep 2016 19:17:36 -0400 Message-ID: <20160922231742.437572192@goodmis.org> References: <20160922231728.394180695@goodmis.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker To: linux-kernel@vger.kernel.org, linux-rt-users Return-path: Content-Disposition: inline; filename=0008-x86-preempt-lazy-fixup-should_resched.patch Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org 3.18.42-rt45-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior should_resched() returns true if NEED_RESCHED is set and the preempt_count is 0 _or_ if NEED_RESCHED_LAZY is set ignoring the preempt counter. Ignoring the preemp counter is wrong. This patch adds this into account. While at it, __preempt_count_dec_and_test() ignores preempt_lazy_count while checking TIF_NEED_RESCHED_LAZY so we this check, too. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt --- arch/x86/include/asm/preempt.h | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index 060d1b4e475d..6806369bddf5 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -95,6 +95,8 @@ static __always_inline bool __preempt_count_dec_and_test(void) if (____preempt_count_dec_and_test()) return true; #ifdef CONFIG_PREEMPT_LAZY + if (current_thread_info()->preempt_lazy_count) + return false; return test_thread_flag(TIF_NEED_RESCHED_LAZY); #else return false; @@ -107,8 +109,18 @@ static __always_inline bool __preempt_count_dec_and_test(void) static __always_inline bool should_resched(void) { #ifdef CONFIG_PREEMPT_LAZY - return unlikely(!raw_cpu_read_4(__preempt_count) || \ - test_thread_flag(TIF_NEED_RESCHED_LAZY)); + u32 tmp; + + if (!raw_cpu_read_4(__preempt_count)) + return true; + + /* preempt count == 0 ? */ + tmp &= ~PREEMPT_NEED_RESCHED; + if (tmp) + return false; + if (current_thread_info()->preempt_lazy_count) + return false; + return test_thread_flag(TIF_NEED_RESCHED_LAZY); #else return unlikely(!raw_cpu_read_4(__preempt_count)); #endif -- 2.8.1