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Subject: powerpc: Add support for lazy preemption
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu Nov 1 10:14:11 2012 +0100
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.3-rt21.tar.xz
From: Thomas Gleixner <tglx@linutronix.de>
Implement the powerpc pieces for lazy preempt.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/thread_info.h | 7 +++++++
arch/powerpc/kernel/interrupt.c | 8 ++++++--
3 files changed, 14 insertions(+), 2 deletions(-)
---
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -235,6 +235,7 @@ config PPC
select HAVE_PERF_EVENTS_NMI if PPC64
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_PREEMPT_LAZY
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE
select HAVE_RSEQ
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -47,6 +47,8 @@
struct thread_info {
int preempt_count; /* 0 => preemptable,
<0 => BUG */
+ int preempt_lazy_count; /* 0 => preemptable,
+ <0 => BUG */
unsigned long local_flags; /* private flags for thread */
#ifdef CONFIG_LIVEPATCH
unsigned long *livepatch_sp;
@@ -93,6 +95,7 @@ void arch_setup_new_exec(void);
#define TIF_PATCH_PENDING 6 /* pending live patching update */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SINGLESTEP 8 /* singlestepping active */
+#define TIF_NEED_RESCHED_LAZY 9 /* lazy rescheduling necessary */
#define TIF_SECCOMP 10 /* secure computing */
#define TIF_RESTOREALL 11 /* Restore all regs (implies NOERROR) */
#define TIF_NOERROR 12 /* Force successful syscall return */
@@ -108,6 +111,7 @@ void arch_setup_new_exec(void);
#define TIF_POLLING_NRFLAG 19 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_32BIT 20 /* 32 bit binary */
+
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@@ -119,6 +123,7 @@ void arch_setup_new_exec(void);
#define _TIF_PATCH_PENDING (1<<TIF_PATCH_PENDING)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
+#define _TIF_NEED_RESCHED_LAZY (1<<TIF_NEED_RESCHED_LAZY)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTOREALL (1<<TIF_RESTOREALL)
#define _TIF_NOERROR (1<<TIF_NOERROR)
@@ -132,10 +137,12 @@ void arch_setup_new_exec(void);
_TIF_SYSCALL_EMU)
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
+ _TIF_NEED_RESCHED_LAZY | \
_TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_RESTORE_TM | _TIF_PATCH_PENDING | \
_TIF_NOTIFY_SIGNAL)
#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)
+#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
/* Bits in local_flags */
/* Don't move TLF_NAPPING without adjusting the code in entry_32.S */
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -346,7 +346,7 @@ interrupt_exit_user_prepare_main(unsigne
ti_flags = READ_ONCE(current_thread_info()->flags);
while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
local_irq_enable();
- if (ti_flags & _TIF_NEED_RESCHED) {
+ if (ti_flags & _TIF_NEED_RESCHED_MASK) {
schedule();
} else {
/*
@@ -552,11 +552,15 @@ notrace unsigned long interrupt_exit_ker
/* Returning to a kernel context with local irqs enabled. */
WARN_ON_ONCE(!(regs->msr & MSR_EE));
again:
- if (IS_ENABLED(CONFIG_PREEMPT)) {
+ if (IS_ENABLED(CONFIG_PREEMPTION)) {
/* Return to preemptible kernel context */
if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED)) {
if (preempt_count() == 0)
preempt_schedule_irq();
+ } else if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED_LAZY)) {
+ if ((preempt_count() == 0) &&
+ (current_thread_info()->preempt_lazy_count == 0))
+ preempt_schedule_irq();
}
}
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