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-rw-r--r--debian/patches-rt/0263-arch-arm64-Add-lazy-preempt-support.patch168
1 files changed, 168 insertions, 0 deletions
diff --git a/debian/patches-rt/0263-arch-arm64-Add-lazy-preempt-support.patch b/debian/patches-rt/0263-arch-arm64-Add-lazy-preempt-support.patch
new file mode 100644
index 000000000..bf46cf898
--- /dev/null
+++ b/debian/patches-rt/0263-arch-arm64-Add-lazy-preempt-support.patch
@@ -0,0 +1,168 @@
+From 7499fc472caecd0270f69d5857ca8a53cc6dad83 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 263/323] arch/arm64: Add lazy preempt support
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.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: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
+---
+ arch/arm64/Kconfig | 1 +
+ arch/arm64/include/asm/preempt.h | 25 ++++++++++++++++++++++++-
+ arch/arm64/include/asm/thread_info.h | 6 +++++-
+ arch/arm64/kernel/asm-offsets.c | 1 +
+ arch/arm64/kernel/entry.S | 13 +++++++++++--
+ arch/arm64/kernel/signal.c | 2 +-
+ 6 files changed, 43 insertions(+), 5 deletions(-)
+
+diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
+index 13cf137da999..7681d7b65c7d 100644
+--- a/arch/arm64/Kconfig
++++ b/arch/arm64/Kconfig
+@@ -173,6 +173,7 @@ config ARM64
+ select HAVE_PERF_EVENTS
+ select HAVE_PERF_REGS
+ select HAVE_PERF_USER_STACK_DUMP
++ select HAVE_PREEMPT_LAZY
+ select HAVE_REGS_AND_STACK_ACCESS_API
+ select HAVE_FUNCTION_ARG_ACCESS_API
+ select HAVE_FUTEX_CMPXCHG if FUTEX
+diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
+index f1486b32502c..7a5770d825b9 100644
+--- a/arch/arm64/include/asm/preempt.h
++++ b/arch/arm64/include/asm/preempt.h
+@@ -70,13 +70,36 @@ 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 cdcf307764aa..6eb36a2126e8 100644
+--- a/arch/arm64/include/asm/thread_info.h
++++ b/arch/arm64/include/asm/thread_info.h
+@@ -29,6 +29,7 @@ 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 {
+@@ -74,6 +75,7 @@ void arch_release_task_struct(struct task_struct *tsk);
+ #define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
+ #define TIF_SECCOMP 11 /* syscall secure computing */
+ #define TIF_SYSCALL_EMU 12 /* syscall emulation active */
++#define TIF_NEED_RESCHED_LAZY 13
+ #define TIF_MEMDIE 18 /* is terminating due to OOM killer */
+ #define TIF_FREEZE 19
+ #define TIF_RESTORE_SIGMASK 20
+@@ -99,13 +101,15 @@ void arch_release_task_struct(struct task_struct *tsk);
+ #define _TIF_32BIT (1 << TIF_32BIT)
+ #define _TIF_SVE (1 << TIF_SVE)
+ #define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT)
++#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
+ #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
+
+ #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
+ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
+ _TIF_UPROBE | _TIF_FSCHECK | _TIF_MTE_ASYNC_FAULT | \
+- _TIF_NOTIFY_SIGNAL)
++ _TIF_NEED_RESCHED_LAZY | _TIF_NOTIFY_SIGNAL)
+
++#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
+ #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
+ _TIF_SYSCALL_EMU)
+diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
+index 7d32fc959b1a..b2f29bd2ae87 100644
+--- a/arch/arm64/kernel/asm-offsets.c
++++ b/arch/arm64/kernel/asm-offsets.c
+@@ -30,6 +30,7 @@ int main(void)
+ BLANK();
+ 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));
+ DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit));
+ #ifdef CONFIG_ARM64_SW_TTBR0_PAN
+ DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
+diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
+index a94acea770c7..0bfa079043f8 100644
+--- a/arch/arm64/kernel/entry.S
++++ b/arch/arm64/kernel/entry.S
+@@ -523,9 +523,18 @@ alternative_if ARM64_HAS_IRQ_PRIO_MASKING
+ mrs x0, daif
+ orr x24, x24, x0
+ alternative_else_nop_endif
+- cbnz x24, 1f // preempt count != 0 || NMI return path
+- bl arm64_preempt_schedule_irq // irq en/disable is done inside
++
++ cbz x24, 1f // (need_resched + count) == 0
++ cbnz w24, 2f // count != 0
++
++ ldr w24, [tsk, #TSK_TI_PREEMPT_LAZY] // get preempt lazy count
++ cbnz w24, 2f // preempt lazy count != 0
++
++ ldr x0, [tsk, #TSK_TI_FLAGS] // get flags
++ tbz x0, #TIF_NEED_RESCHED_LAZY, 2f // needs rescheduling?
+ 1:
++ bl arm64_preempt_schedule_irq // irq en/disable is done inside
++2:
+ #endif
+
+ mov x0, sp
+diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
+index b6fbbd527dd7..94eed0dc3afc 100644
+--- a/arch/arm64/kernel/signal.c
++++ b/arch/arm64/kernel/signal.c
+@@ -921,7 +921,7 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
+ /* Check valid user FS if needed */
+ addr_limit_user_check();
+
+- 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
+