linux-kernel - [PATCH 3/5] sched/preempt: Prepare for supporting !CONFIG_GENERIC

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Message-Id: <20211220140142.922323-4-frederic@kernel.org>
Date:   Mon, 20 Dec 2021 15:01:40 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        James Morse <james.morse@....com>,
        David Laight <David.Laight@...LAB.COM>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 3/5] sched/preempt: Prepare for supporting !CONFIG_GENERIC_ENTRY dynamic preemption

There is no need to force dynamic preemption to depend on the generic
entry code. The latter is convenient but not mandatory. An architecture
that doesn't support it just need to provide a static call on its
kernel IRQ exit preemption path.

Prepare the preempt dynamic code to handle that.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Quentin Perret <qperret@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: James Morse <james.morse@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: David Laight <David.Laight@...LAB.COM>
Cc: Kees Cook <keescook@...omium.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 arch/Kconfig                 | 1 -
 include/linux/entry-common.h | 3 ++-
 kernel/sched/core.c          | 6 ++++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 26b8ed11639d..f3fb543d5da0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1266,7 +1266,6 @@ config HAVE_STATIC_CALL_INLINE
 config HAVE_PREEMPT_DYNAMIC
 	bool
 	depends on HAVE_STATIC_CALL
-	depends on GENERIC_ENTRY
 	help
 	   Select this if the architecture support boot time preempt setting
 	   on top of static calls. It is strongly advised to support inline
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 2e2b8d6140ed..81166bbc0f22 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -456,7 +456,8 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
  */
 void irqentry_exit_cond_resched(void);
 #ifdef CONFIG_PREEMPT_DYNAMIC
-DECLARE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+#define __irqentry_exit_cond_resched_func irqentry_exit_cond_resched
+DECLARE_STATIC_CALL(irqentry_exit_cond_resched, __irqentry_exit_cond_resched_func);
 #endif
 
 /**
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fe53e510e711..865b0fc0ac04 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6553,7 +6553,9 @@ EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
 
+#ifdef CONFIG_GENERIC_ENTRY
 #include <linux/entry-common.h>
+#endif
 
 /*
  * SC:cond_resched
@@ -6618,7 +6620,7 @@ void sched_dynamic_update(int mode)
 	static_call_update(might_resched, __cond_resched);
 	static_call_update(preempt_schedule, __preempt_schedule_func);
 	static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
-	static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+	static_call_update(irqentry_exit_cond_resched, __irqentry_exit_cond_resched_func);
 
 	switch (mode) {
 	case preempt_dynamic_none:
@@ -6644,7 +6646,7 @@ void sched_dynamic_update(int mode)
 		static_call_update(might_resched, (void *)&__static_call_return0);
 		static_call_update(preempt_schedule, __preempt_schedule_func);
 		static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
-		static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+		static_call_update(irqentry_exit_cond_resched, __irqentry_exit_cond_resched_func);
 		pr_info("Dynamic Preempt: full\n");
 		break;
 	}
-- 
2.25.1