summaryrefslogtreecommitdiffstats
path: root/debian/patches-rt/0260-x86-Support-for-lazy-preemption.patch
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--debian/patches-rt/0260-x86-Support-for-lazy-preemption.patch171
1 files changed, 171 insertions, 0 deletions
diff --git a/debian/patches-rt/0260-x86-Support-for-lazy-preemption.patch b/debian/patches-rt/0260-x86-Support-for-lazy-preemption.patch
new file mode 100644
index 000000000..1b4da37ab
--- /dev/null
+++ b/debian/patches-rt/0260-x86-Support-for-lazy-preemption.patch
@@ -0,0 +1,171 @@
+From 3e75dc5bbc430b2a1db27fe101ed508b067af7b0 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Thu, 1 Nov 2012 11:03:47 +0100
+Subject: [PATCH 260/323] x86: Support for lazy preemption
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+Implement the x86 pieces for lazy preempt.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
+---
+ arch/x86/Kconfig | 1 +
+ arch/x86/include/asm/preempt.h | 33 +++++++++++++++++++++++++++++-
+ arch/x86/include/asm/thread_info.h | 11 ++++++++++
+ include/linux/entry-common.h | 6 +++---
+ kernel/entry/common.c | 2 +-
+ 5 files changed, 48 insertions(+), 5 deletions(-)
+
+diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
+index c72d66a0e840..b9f68b01a8c8 100644
+--- a/arch/x86/Kconfig
++++ b/arch/x86/Kconfig
+@@ -213,6 +213,7 @@ config X86
+ select HAVE_PCI
+ select HAVE_PERF_REGS
+ select HAVE_PERF_USER_STACK_DUMP
++ select HAVE_PREEMPT_LAZY
+ select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
+ select HAVE_POSIX_CPU_TIMERS_TASK_WORK
+ select HAVE_REGS_AND_STACK_ACCESS_API
+diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
+index 50e0c0ab7b97..afe37a8c6c24 100644
+--- a/arch/x86/include/asm/preempt.h
++++ b/arch/x86/include/asm/preempt.h
+@@ -89,17 +89,48 @@ static __always_inline void __preempt_count_sub(int val)
+ * a decrement which hits zero means we have no preempt_count and should
+ * reschedule.
+ */
+-static __always_inline bool __preempt_count_dec_and_test(void)
++static __always_inline bool ____preempt_count_dec_and_test(void)
+ {
+ return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var]));
+ }
+
++static __always_inline bool __preempt_count_dec_and_test(void)
++{
++ if (____preempt_count_dec_and_test())
++ return true;
++#ifdef CONFIG_PREEMPT_LAZY
++ if (preempt_count())
++ return false;
++ if (current_thread_info()->preempt_lazy_count)
++ return false;
++ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
++#else
++ return false;
++#endif
++}
++
+ /*
+ * Returns true when we need to resched and can (barring IRQ state).
+ */
+ static __always_inline bool should_resched(int preempt_offset)
+ {
++#ifdef CONFIG_PREEMPT_LAZY
++ u32 tmp;
++ tmp = raw_cpu_read_4(__preempt_count);
++ if (tmp == preempt_offset)
++ return true;
++
++ /* preempt count == 0 ? */
++ tmp &= ~PREEMPT_NEED_RESCHED;
++ if (tmp != preempt_offset)
++ return false;
++ /* XXX PREEMPT_LOCK_OFFSET */
++ if (current_thread_info()->preempt_lazy_count)
++ return false;
++ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
++#else
+ return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
++#endif
+ }
+
+ #ifdef CONFIG_PREEMPTION
+diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
+index 012c8ee93b67..d77e99ba7610 100644
+--- a/arch/x86/include/asm/thread_info.h
++++ b/arch/x86/include/asm/thread_info.h
+@@ -56,17 +56,24 @@ struct task_struct;
+ struct thread_info {
+ unsigned long flags; /* low level flags */
+ u32 status; /* thread synchronous flags */
++ int preempt_lazy_count; /* 0 => lazy preemptable
++ <0 => BUG */
+ };
+
+ #define INIT_THREAD_INFO(tsk) \
+ { \
+ .flags = 0, \
++ .preempt_lazy_count = 0, \
+ }
+
+ #else /* !__ASSEMBLY__ */
+
+ #include <asm/asm-offsets.h>
+
++#define GET_THREAD_INFO(reg) \
++ _ASM_MOV PER_CPU_VAR(cpu_current_top_of_stack),reg ; \
++ _ASM_SUB $(THREAD_SIZE),reg ;
++
+ #endif
+
+ /*
+@@ -103,6 +110,7 @@ struct thread_info {
+ #define TIF_SYSCALL_TRACEPOINT 28 /* syscall tracepoint instrumentation */
+ #define TIF_ADDR32 29 /* 32-bit address space on 64 bits */
+ #define TIF_X32 30 /* 32-bit native x86-64 binary */
++#define TIF_NEED_RESCHED_LAZY 31 /* lazy rescheduling necessary */
+
+ #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
+ #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
+@@ -124,6 +132,7 @@ struct thread_info {
+ #define _TIF_IA32 (1 << TIF_IA32)
+ #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
+ #define _TIF_SLD (1 << TIF_SLD)
++#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
+ #define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
+ #define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP)
+ #define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
+@@ -156,6 +165,8 @@ struct thread_info {
+
+ #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
+
++#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
++
+ #define STACK_WARN (THREAD_SIZE/8)
+
+ /*
+diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
+index 46c42479f950..b902af13d05f 100644
+--- a/include/linux/entry-common.h
++++ b/include/linux/entry-common.h
+@@ -67,9 +67,9 @@
+ # define ARCH_EXIT_TO_USER_MODE_WORK (0)
+ #endif
+
+-#define EXIT_TO_USER_MODE_WORK \
+- (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
+- _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
++#define EXIT_TO_USER_MODE_WORK \
++ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
++ _TIF_NEED_RESCHED_MASK | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
+ ARCH_EXIT_TO_USER_MODE_WORK)
+
+ /**
+diff --git a/kernel/entry/common.c b/kernel/entry/common.c
+index f32250adb681..cdf97ea30b4c 100644
+--- a/kernel/entry/common.c
++++ b/kernel/entry/common.c
+@@ -157,7 +157,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
+
+ local_irq_enable_exit_to_user(ti_work);
+
+- if (ti_work & _TIF_NEED_RESCHED)
++ if (ti_work & _TIF_NEED_RESCHED_MASK)
+ schedule();
+
+ #ifdef ARCH_RT_DELAYS_SIGNAL_SEND
+--
+2.43.0
+