146 lines
5.6 KiB
Diff
146 lines
5.6 KiB
Diff
From 87fb6813fa0a5ecff7fd2c657b37cfe97733ae90 Mon Sep 17 00:00:00 2001
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From: Anders Roxell <anders.roxell@linaro.org>
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Date: Thu, 14 May 2015 17:52:17 +0200
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Subject: [PATCH 38/62] arch/arm64: Add lazy preempt support
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arm64 is missing support for PREEMPT_RT. The main feature which is
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lacking is support for lazy preemption. The arch-specific entry code,
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thread information structure definitions, and associated data tables
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have to be extended to provide this support. Then the Kconfig file has
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to be extended to indicate the support is available, and also to
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indicate that support for full RT preemption is now available.
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Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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arch/arm64/Kconfig | 1 +
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arch/arm64/include/asm/preempt.h | 25 ++++++++++++++++++++++++-
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arch/arm64/include/asm/thread_info.h | 8 +++++++-
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arch/arm64/kernel/asm-offsets.c | 1 +
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arch/arm64/kernel/signal.c | 2 +-
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5 files changed, 34 insertions(+), 3 deletions(-)
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diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
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index ea70eb960565..6e16670a7f43 100644
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--- a/arch/arm64/Kconfig
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+++ b/arch/arm64/Kconfig
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@@ -199,6 +199,7 @@ config ARM64
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select HAVE_PERF_USER_STACK_DUMP
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select HAVE_PREEMPT_DYNAMIC_KEY
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select HAVE_REGS_AND_STACK_ACCESS_API
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+ select HAVE_PREEMPT_LAZY
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select HAVE_POSIX_CPU_TIMERS_TASK_WORK
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select HAVE_FUNCTION_ARG_ACCESS_API
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select MMU_GATHER_RCU_TABLE_FREE
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diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
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index 0159b625cc7f..a5486918e5ee 100644
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--- a/arch/arm64/include/asm/preempt.h
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+++ b/arch/arm64/include/asm/preempt.h
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@@ -71,13 +71,36 @@ static inline bool __preempt_count_dec_and_test(void)
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* interrupt occurring between the non-atomic READ_ONCE/WRITE_ONCE
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* pair.
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*/
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- return !pc || !READ_ONCE(ti->preempt_count);
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+ if (!pc || !READ_ONCE(ti->preempt_count))
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+ return true;
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+#ifdef CONFIG_PREEMPT_LAZY
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+ if ((pc & ~PREEMPT_NEED_RESCHED))
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+ return false;
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+ if (current_thread_info()->preempt_lazy_count)
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+ return false;
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+ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
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+#else
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+ return false;
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+#endif
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}
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static inline bool should_resched(int preempt_offset)
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{
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+#ifdef CONFIG_PREEMPT_LAZY
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+ u64 pc = READ_ONCE(current_thread_info()->preempt_count);
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+ if (pc == preempt_offset)
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+ return true;
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+
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+ if ((pc & ~PREEMPT_NEED_RESCHED) != preempt_offset)
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+ return false;
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+
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+ if (current_thread_info()->preempt_lazy_count)
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+ return false;
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+ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
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+#else
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u64 pc = READ_ONCE(current_thread_info()->preempt_count);
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return pc == preempt_offset;
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+#endif
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}
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#ifdef CONFIG_PREEMPTION
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diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
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index 848739c15de8..4b7148fd5551 100644
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--- a/arch/arm64/include/asm/thread_info.h
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+++ b/arch/arm64/include/asm/thread_info.h
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@@ -26,6 +26,7 @@ struct thread_info {
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#ifdef CONFIG_ARM64_SW_TTBR0_PAN
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u64 ttbr0; /* saved TTBR0_EL1 */
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#endif
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+ int preempt_lazy_count; /* 0 => preemptable, <0 => bug */
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union {
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u64 preempt_count; /* 0 => preemptible, <0 => bug */
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struct {
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@@ -68,6 +69,7 @@ int arch_dup_task_struct(struct task_struct *dst,
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#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
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#define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */
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#define TIF_NOTIFY_SIGNAL 6 /* signal notifications exist */
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+#define TIF_NEED_RESCHED_LAZY 7
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#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
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#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
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#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
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@@ -100,8 +102,10 @@ int arch_dup_task_struct(struct task_struct *dst,
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#define _TIF_SVE (1 << TIF_SVE)
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#define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT)
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#define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
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+#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
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-#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
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+#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | \
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+ _TIF_SIGPENDING | \
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_TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
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_TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
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_TIF_NOTIFY_SIGNAL)
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@@ -110,6 +114,8 @@ int arch_dup_task_struct(struct task_struct *dst,
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_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
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_TIF_SYSCALL_EMU)
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+#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
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+
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#ifdef CONFIG_SHADOW_CALL_STACK
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#define INIT_SCS \
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.scs_base = init_shadow_call_stack, \
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diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
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index 1197e7679882..e74c0415f67e 100644
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--- a/arch/arm64/kernel/asm-offsets.c
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+++ b/arch/arm64/kernel/asm-offsets.c
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@@ -32,6 +32,7 @@ int main(void)
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DEFINE(TSK_TI_CPU, offsetof(struct task_struct, thread_info.cpu));
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DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
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DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
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+ DEFINE(TSK_TI_PREEMPT_LAZY, offsetof(struct task_struct, thread_info.preempt_lazy_count));
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#ifdef CONFIG_ARM64_SW_TTBR0_PAN
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DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
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#endif
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diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
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index 82f4572c8ddf..2a606c7bf025 100644
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--- a/arch/arm64/kernel/signal.c
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+++ b/arch/arm64/kernel/signal.c
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@@ -1108,7 +1108,7 @@ static void do_signal(struct pt_regs *regs)
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void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
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{
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do {
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- if (thread_flags & _TIF_NEED_RESCHED) {
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+ if (thread_flags & _TIF_NEED_RESCHED_MASK) {
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/* Unmask Debug and SError for the next task */
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local_daif_restore(DAIF_PROCCTX_NOIRQ);
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--
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2.43.0
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