linux-kernel - [PATCH RT 2/3] riscv: add lazy preempt support

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Message-Id: <20230510162406.1955-3-jszhang@kernel.org>
Date:   Thu, 11 May 2023 00:24:05 +0800
From:   Jisheng Zhang <jszhang@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Schaffner Tobias <tobias.schaffner@...mens.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [PATCH RT 2/3] riscv: add lazy preempt support

Implement the lazy preempt for riscv.

Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
---
 arch/riscv/Kconfig                   | 1 +
 arch/riscv/include/asm/thread_info.h | 5 ++++-
 arch/riscv/kernel/asm-offsets.c      | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 348c0fa1fc8c..89e9d9fb35c4 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -118,6 +118,7 @@ config RISCV
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
+	select HAVE_PREEMPT_LAZY
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RSEQ
 	select HAVE_STACKPROTECTOR
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index e0d202134b44..c5e9223e9b91 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -59,6 +59,7 @@ extern unsigned long spin_shadow_stack;
 struct thread_info {
 	unsigned long		flags;		/* low level flags */
 	int                     preempt_count;  /* 0=>preemptible, <0=>BUG */
+	int			preempt_lazy_count;	/* 0=>preemptible, <0=>BUG */
 	/*
 	 * These stack pointers are overwritten on every system call or
 	 * exception.  SP is also saved to the stack it can be recovered when
@@ -90,6 +91,7 @@ struct thread_info {
  * - pending work-to-be-done flags are in lowest half-word
  * - other flags in upper half-word(s)
  */
+#define TIF_NEED_RESCHED_LAZY	0	/* lazy rescheduling */
 #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
 #define TIF_SIGPENDING		2	/* signal pending */
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
@@ -104,9 +106,10 @@ struct thread_info {
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
+#define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
 
 #define _TIF_WORK_MASK \
 	(_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | \
-	 _TIF_NOTIFY_SIGNAL | _TIF_UPROBE)
+	 _TIF_NEED_RESCHED_LAZY | _TIF_NOTIFY_SIGNAL | _TIF_UPROBE)
 
 #endif /* _ASM_RISCV_THREAD_INFO_H */
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index d6a75aac1d27..1f8cccacb44e 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -36,6 +36,7 @@ void asm_offsets(void)
 	OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]);
 	OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags);
 	OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
+	OFFSET(TASK_TI_PREEMPT_LAZY_COUNT, task_struct, thread_info.preempt_lazy_count);
 	OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
 	OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp);
 
-- 
2.40.1