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From 8e5e88a7528b5f0b0f2b9835deaf8b6db693500f Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 1 Nov 2012 10:14:11 +0100
Subject: [PATCH 262/323] powerpc: Add 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 powerpc pieces for lazy preempt.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/thread_info.h | 16 ++++++++++++----
arch/powerpc/kernel/asm-offsets.c | 1 +
arch/powerpc/kernel/entry_32.S | 23 ++++++++++++++++-------
arch/powerpc/kernel/exceptions-64e.S | 16 ++++++++++++----
arch/powerpc/kernel/syscall_64.c | 10 +++++++---
6 files changed, 49 insertions(+), 18 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b3ab6c2d9f66..6d8ce54ad6dd 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -230,6 +230,7 @@ config PPC
select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !HAVE_HARDLOCKUP_DETECTOR_ARCH
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_PREEMPT_LAZY
select MMU_GATHER_RCU_TABLE_FREE
select MMU_GATHER_PAGE_SIZE
select HAVE_REGS_AND_STACK_ACCESS_API
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index ff31d2fa2140..23bfe231fda3 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -54,6 +54,8 @@
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;
@@ -104,11 +106,12 @@ void arch_setup_new_exec(void);
#define TIF_SINGLESTEP 8 /* singlestepping active */
#define TIF_NOHZ 9 /* in adaptive nohz mode */
#define TIF_SECCOMP 10 /* secure computing */
-#define TIF_RESTOREALL 11 /* Restore all regs (implies NOERROR) */
-#define TIF_NOERROR 12 /* Force successful syscall return */
+
+#define TIF_NEED_RESCHED_LAZY 11 /* lazy rescheduling necessary */
+#define TIF_SYSCALL_TRACEPOINT 12 /* syscall tracepoint instrumentation */
+
#define TIF_NOTIFY_RESUME 13 /* callback before returning to user */
#define TIF_UPROBE 14 /* breakpointed or single-stepping */
-#define TIF_SYSCALL_TRACEPOINT 15 /* syscall tracepoint instrumentation */
#define TIF_EMULATE_STACK_STORE 16 /* Is an instruction emulation
for stack store? */
#define TIF_MEMDIE 17 /* is terminating due to OOM killer */
@@ -117,6 +120,9 @@ void arch_setup_new_exec(void);
#endif
#define TIF_POLLING_NRFLAG 19 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_32BIT 20 /* 32 bit binary */
+#define TIF_RESTOREALL 21 /* Restore all regs (implies NOERROR) */
+#define TIF_NOERROR 22 /* Force successful syscall return */
+
/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -137,6 +143,7 @@ void arch_setup_new_exec(void);
#define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT)
#define _TIF_EMULATE_STACK_STORE (1<<TIF_EMULATE_STACK_STORE)
#define _TIF_NOHZ (1<<TIF_NOHZ)
+#define _TIF_NEED_RESCHED_LAZY (1<<TIF_NEED_RESCHED_LAZY)
#define _TIF_SYSCALL_EMU (1<<TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_DOTRACE (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \
@@ -145,8 +152,9 @@ void arch_setup_new_exec(void);
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
_TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_RESTORE_TM | _TIF_PATCH_PENDING | \
- _TIF_NOTIFY_SIGNAL)
+ _TIF_NEED_RESCHED_LAZY | _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 */
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 5c125255571c..597379121407 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -189,6 +189,7 @@ int main(void)
OFFSET(TI_FLAGS, thread_info, flags);
OFFSET(TI_LOCAL_FLAGS, thread_info, local_flags);
OFFSET(TI_PREEMPT, thread_info, preempt_count);
+ OFFSET(TI_PREEMPT_LAZY, thread_info, preempt_lazy_count);
#ifdef CONFIG_PPC64
OFFSET(DCACHEL1BLOCKSIZE, ppc64_caches, l1d.block_size);
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 459f5d00b990..fc9517a97640 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -414,7 +414,9 @@ ret_from_syscall:
mtmsr r10
lwz r9,TI_FLAGS(r2)
li r8,-MAX_ERRNO
- andi. r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
+ lis r0,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)@h
+ ori r0,r0, (_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)@l
+ and. r0,r9,r0
bne- syscall_exit_work
cmplw 0,r3,r8
blt+ syscall_exit_cont
@@ -530,13 +532,13 @@ syscall_dotrace:
b syscall_dotrace_cont
syscall_exit_work:
- andi. r0,r9,_TIF_RESTOREALL
+ andis. r0,r9,_TIF_RESTOREALL@h
beq+ 0f
REST_NVGPRS(r1)
b 2f
0: cmplw 0,r3,r8
blt+ 1f
- andi. r0,r9,_TIF_NOERROR
+ andis. r0,r9,_TIF_NOERROR@h
bne- 1f
lwz r11,_CCR(r1) /* Load CR */
neg r3,r3
@@ -545,12 +547,12 @@ syscall_exit_work:
1: stw r6,RESULT(r1) /* Save result */
stw r3,GPR3(r1) /* Update return value */
-2: andi. r0,r9,(_TIF_PERSYSCALL_MASK)
+2: andis. r0,r9,(_TIF_PERSYSCALL_MASK)@h
beq 4f
/* Clear per-syscall TIF flags if any are set. */
- li r11,_TIF_PERSYSCALL_MASK
+ lis r11,(_TIF_PERSYSCALL_MASK)@h
addi r12,r2,TI_FLAGS
3: lwarx r8,0,r12
andc r8,r8,r11
@@ -927,7 +929,14 @@ resume_kernel:
cmpwi 0,r0,0 /* if non-zero, just restore regs and return */
bne restore_kuap
andi. r8,r8,_TIF_NEED_RESCHED
+ bne+ 1f
+ lwz r0,TI_PREEMPT_LAZY(r2)
+ cmpwi 0,r0,0 /* if non-zero, just restore regs and return */
+ bne restore_kuap
+ lwz r0,TI_FLAGS(r2)
+ andi. r0,r0,_TIF_NEED_RESCHED_LAZY
beq+ restore_kuap
+1:
lwz r3,_MSR(r1)
andi. r0,r3,MSR_EE /* interrupts off? */
beq restore_kuap /* don't schedule if so */
@@ -1248,7 +1257,7 @@ global_dbcr0:
#endif /* !(CONFIG_4xx || CONFIG_BOOKE) */
do_work: /* r10 contains MSR_KERNEL here */
- andi. r0,r9,_TIF_NEED_RESCHED
+ andi. r0,r9,_TIF_NEED_RESCHED_MASK
beq do_user_signal
do_resched: /* r10 contains MSR_KERNEL here */
@@ -1267,7 +1276,7 @@ recheck:
LOAD_REG_IMMEDIATE(r10,MSR_KERNEL)
mtmsr r10 /* disable interrupts */
lwz r9,TI_FLAGS(r2)
- andi. r0,r9,_TIF_NEED_RESCHED
+ andi. r0,r9,_TIF_NEED_RESCHED_MASK
bne- do_resched
andi. r0,r9,_TIF_USER_WORK_MASK
beq restore_user
diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index f579ce46eef2..715ff292a8f8 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -1080,7 +1080,7 @@ _GLOBAL(ret_from_except_lite)
li r10, -1
mtspr SPRN_DBSR,r10
b restore
-1: andi. r0,r4,_TIF_NEED_RESCHED
+1: andi. r0,r4,_TIF_NEED_RESCHED_MASK
beq 2f
bl restore_interrupts
SCHEDULE_USER
@@ -1132,12 +1132,20 @@ resume_kernel:
bne- 0b
1:
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
/* Check if we need to preempt */
+ lwz r8,TI_PREEMPT(r9)
+ cmpwi 0,r8,0 /* if non-zero, just restore regs and return */
+ bne restore
andi. r0,r4,_TIF_NEED_RESCHED
+ bne+ check_count
+
+ andi. r0,r4,_TIF_NEED_RESCHED_LAZY
beq+ restore
+ lwz r8,TI_PREEMPT_LAZY(r9)
+
/* Check that preempt_count() == 0 and interrupts are enabled */
- lwz r8,TI_PREEMPT(r9)
+check_count:
cmpwi cr0,r8,0
bne restore
ld r0,SOFTE(r1)
@@ -1158,7 +1166,7 @@ resume_kernel:
* interrupted after loading SRR0/1.
*/
wrteei 0
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPTION */
restore:
/*
diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 310bcd768cd5..ae3212dcf562 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -193,7 +193,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
ti_flags = READ_ONCE(*ti_flagsp);
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 {
/*
@@ -277,7 +277,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
ti_flags = READ_ONCE(*ti_flagsp);
while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
local_irq_enable(); /* returning to user: may enable */
- if (ti_flags & _TIF_NEED_RESCHED) {
+ if (ti_flags & _TIF_NEED_RESCHED_MASK) {
schedule();
} else {
if (ti_flags & _TIF_SIGPENDING)
@@ -361,11 +361,15 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
/* 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(*ti_flagsp & _TIF_NEED_RESCHED)) {
if (preempt_count() == 0)
preempt_schedule_irq();
+ } else if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED_LAZY)) {
+ if ((preempt_count() == 0) &&
+ (current_thread_info()->preempt_lazy_count == 0))
+ preempt_schedule_irq();
}
}
--
2.43.0
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