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-rw-r--r--debian/patches-rt/0038-arch-arm64-Add-lazy-preempt-support.patch146
1 files changed, 146 insertions, 0 deletions
diff --git a/debian/patches-rt/0038-arch-arm64-Add-lazy-preempt-support.patch b/debian/patches-rt/0038-arch-arm64-Add-lazy-preempt-support.patch
new file mode 100644
index 000000000..4df0c8a40
--- /dev/null
+++ b/debian/patches-rt/0038-arch-arm64-Add-lazy-preempt-support.patch
@@ -0,0 +1,146 @@
+From 12a36ad989490f5ae3ed6a50d764385e8e27e024 Mon Sep 17 00:00:00 2001
+From: Anders Roxell <anders.roxell@linaro.org>
+Date: Thu, 14 May 2015 17:52:17 +0200
+Subject: [PATCH 38/62] arch/arm64: Add lazy preempt support
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz
+
+arm64 is missing support for PREEMPT_RT. The main feature which is
+lacking is support for lazy preemption. The arch-specific entry code,
+thread information structure definitions, and associated data tables
+have to be extended to provide this support. Then the Kconfig file has
+to be extended to indicate the support is available, and also to
+indicate that support for full RT preemption is now available.
+
+Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+---
+ arch/arm64/Kconfig | 1 +
+ arch/arm64/include/asm/preempt.h | 25 ++++++++++++++++++++++++-
+ arch/arm64/include/asm/thread_info.h | 8 +++++++-
+ arch/arm64/kernel/asm-offsets.c | 1 +
+ arch/arm64/kernel/signal.c | 2 +-
+ 5 files changed, 34 insertions(+), 3 deletions(-)
+
+diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
+index ea70eb960565..6e16670a7f43 100644
+--- a/arch/arm64/Kconfig
++++ b/arch/arm64/Kconfig
+@@ -199,6 +199,7 @@ config ARM64
+ select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_PREEMPT_DYNAMIC_KEY
+ select HAVE_REGS_AND_STACK_ACCESS_API
++ select HAVE_PREEMPT_LAZY
+ select HAVE_POSIX_CPU_TIMERS_TASK_WORK
+ select HAVE_FUNCTION_ARG_ACCESS_API
+ select MMU_GATHER_RCU_TABLE_FREE
+diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
+index 0159b625cc7f..a5486918e5ee 100644
+--- a/arch/arm64/include/asm/preempt.h
++++ b/arch/arm64/include/asm/preempt.h
+@@ -71,13 +71,36 @@ static inline bool __preempt_count_dec_and_test(void)
+ * interrupt occurring between the non-atomic READ_ONCE/WRITE_ONCE
+ * pair.
+ */
+- return !pc || !READ_ONCE(ti->preempt_count);
++ if (!pc || !READ_ONCE(ti->preempt_count))
++ return true;
++#ifdef CONFIG_PREEMPT_LAZY
++ if ((pc & ~PREEMPT_NEED_RESCHED))
++ return false;
++ if (current_thread_info()->preempt_lazy_count)
++ return false;
++ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
++#else
++ return false;
++#endif
+ }
+
+ static inline bool should_resched(int preempt_offset)
+ {
++#ifdef CONFIG_PREEMPT_LAZY
++ u64 pc = READ_ONCE(current_thread_info()->preempt_count);
++ if (pc == preempt_offset)
++ return true;
++
++ if ((pc & ~PREEMPT_NEED_RESCHED) != preempt_offset)
++ return false;
++
++ if (current_thread_info()->preempt_lazy_count)
++ return false;
++ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
++#else
+ u64 pc = READ_ONCE(current_thread_info()->preempt_count);
+ return pc == preempt_offset;
++#endif
+ }
+
+ #ifdef CONFIG_PREEMPTION
+diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
+index 848739c15de8..4b7148fd5551 100644
+--- a/arch/arm64/include/asm/thread_info.h
++++ b/arch/arm64/include/asm/thread_info.h
+@@ -26,6 +26,7 @@ struct thread_info {
+ #ifdef CONFIG_ARM64_SW_TTBR0_PAN
+ u64 ttbr0; /* saved TTBR0_EL1 */
+ #endif
++ int preempt_lazy_count; /* 0 => preemptable, <0 => bug */
+ union {
+ u64 preempt_count; /* 0 => preemptible, <0 => bug */
+ struct {
+@@ -68,6 +69,7 @@ int arch_dup_task_struct(struct task_struct *dst,
+ #define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
+ #define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */
+ #define TIF_NOTIFY_SIGNAL 6 /* signal notifications exist */
++#define TIF_NEED_RESCHED_LAZY 7
+ #define TIF_SYSCALL_TRACE 8 /* syscall trace active */
+ #define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
+ #define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
+@@ -100,8 +102,10 @@ int arch_dup_task_struct(struct task_struct *dst,
+ #define _TIF_SVE (1 << TIF_SVE)
+ #define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT)
+ #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
++#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
+
+-#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
++#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | \
++ _TIF_SIGPENDING | \
+ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
+ _TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
+ _TIF_NOTIFY_SIGNAL)
+@@ -110,6 +114,8 @@ int arch_dup_task_struct(struct task_struct *dst,
+ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
+ _TIF_SYSCALL_EMU)
+
++#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
++
+ #ifdef CONFIG_SHADOW_CALL_STACK
+ #define INIT_SCS \
+ .scs_base = init_shadow_call_stack, \
+diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
+index 1197e7679882..e74c0415f67e 100644
+--- a/arch/arm64/kernel/asm-offsets.c
++++ b/arch/arm64/kernel/asm-offsets.c
+@@ -32,6 +32,7 @@ int main(void)
+ DEFINE(TSK_TI_CPU, offsetof(struct task_struct, thread_info.cpu));
+ DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
+ DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
++ DEFINE(TSK_TI_PREEMPT_LAZY, offsetof(struct task_struct, thread_info.preempt_lazy_count));
+ #ifdef CONFIG_ARM64_SW_TTBR0_PAN
+ DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
+ #endif
+diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
+index 82f4572c8ddf..2a606c7bf025 100644
+--- a/arch/arm64/kernel/signal.c
++++ b/arch/arm64/kernel/signal.c
+@@ -1108,7 +1108,7 @@ static void do_signal(struct pt_regs *regs)
+ void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
+ {
+ do {
+- if (thread_flags & _TIF_NEED_RESCHED) {
++ if (thread_flags & _TIF_NEED_RESCHED_MASK) {
+ /* Unmask Debug and SError for the next task */
+ local_daif_restore(DAIF_PROCCTX_NOIRQ);
+
+--
+2.43.0
+