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linux/debian/patches/features/all/rt/x86-preempt-lazy.patch

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Subject: x86-preempt-lazy.patch
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 01 Nov 2012 11:03:47 +0100
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/patches-3.14.0-rt1.tar.xz
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/thread_info.h | 6 ++++++
arch/x86/kernel/asm-offsets.c | 1 +
arch/x86/kernel/entry_32.S | 17 +++++++++++++++--
arch/x86/kernel/entry_64.S | 28 ++++++++++++++++++++--------
5 files changed, 43 insertions(+), 10 deletions(-)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -21,6 +21,7 @@ config X86_64
### Arch settings
config X86
def_bool y
+ select HAVE_PREEMPT_LAZY
select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -29,6 +29,8 @@ struct thread_info {
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
int saved_preempt_count;
+ int preempt_lazy_count; /* 0 => lazy preemptable
+ <0 => BUG */
mm_segment_t addr_limit;
struct restart_block restart_block;
void __user *sysenter_return;
@@ -80,6 +82,7 @@ struct thread_info {
#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
+#define TIF_NEED_RESCHED_LAZY 9 /* lazy rescheduling necessary */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_UPROBE 12 /* breakpointed or singlestepping */
@@ -104,6 +107,7 @@ struct thread_info {
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
+#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
#define _TIF_MCE_NOTIFY (1 << TIF_MCE_NOTIFY)
#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
@@ -153,6 +157,8 @@ struct thread_info {
#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
+#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
+
#ifdef CONFIG_X86_32
#define STACK_WARN (THREAD_SIZE/8)
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -32,6 +32,7 @@ void common(void) {
OFFSET(TI_flags, thread_info, flags);
OFFSET(TI_status, thread_info, status);
OFFSET(TI_addr_limit, thread_info, addr_limit);
+ OFFSET(TI_preempt_lazy_count, thread_info, preempt_lazy_count);
BLANK();
OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -363,8 +363,21 @@ END(ret_from_exception)
ENTRY(resume_kernel)
DISABLE_INTERRUPTS(CLBR_ANY)
need_resched:
+ # preempt count == 0 + NEED_RS set?
cmpl $0,PER_CPU_VAR(__preempt_count)
+ jz test_int_off
+
+ # atleast preempt count == 0 ?
+ cmpl $_TIF_NEED_RESCHED,PER_CPU_VAR(__preempt_count)
+ jne restore_all
+
+ cmpl $0,TI_preempt_lazy_count(%ebp) # non-zero preempt_lazy_count ?
jnz restore_all
+
+ testl $_TIF_NEED_RESCHED_LAZY, %ecx
+ jz restore_all
+
+test_int_off:
testl $X86_EFLAGS_IF,PT_EFLAGS(%esp) # interrupts off (exception path) ?
jz restore_all
call preempt_schedule_irq
@@ -604,7 +617,7 @@ ENDPROC(system_call)
ALIGN
RING0_PTREGS_FRAME # can't unwind into user space anyway
work_pending:
- testb $_TIF_NEED_RESCHED, %cl
+ testl $_TIF_NEED_RESCHED_MASK, %ecx
jz work_notifysig
work_resched:
call schedule
@@ -617,7 +630,7 @@ ENDPROC(system_call)
andl $_TIF_WORK_MASK, %ecx # is there any work to be done other
# than syscall tracing?
jz restore_all
- testb $_TIF_NEED_RESCHED, %cl
+ testl $_TIF_NEED_RESCHED_MASK, %ecx
jnz work_resched
work_notifysig: # deal with pending signals and
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -658,8 +658,8 @@ GLOBAL(system_call_after_swapgs)
/* Handle reschedules */
/* edx: work, edi: workmask */
sysret_careful:
- bt $TIF_NEED_RESCHED,%edx
- jnc sysret_signal
+ testl $_TIF_NEED_RESCHED_MASK,%edx
+ jz sysret_signal
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
@@ -771,8 +771,8 @@ GLOBAL(int_with_check)
/* First do a reschedule test. */
/* edx: work, edi: workmask */
int_careful:
- bt $TIF_NEED_RESCHED,%edx
- jnc int_very_careful
+ testl $_TIF_NEED_RESCHED_MASK,%edx
+ jz int_very_careful
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
@@ -1071,8 +1071,8 @@ ENTRY(native_iret)
/* edi: workmask, edx: work */
retint_careful:
CFI_RESTORE_STATE
- bt $TIF_NEED_RESCHED,%edx
- jnc retint_signal
+ testl $_TIF_NEED_RESCHED_MASK,%edx
+ jz retint_signal
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
@@ -1104,7 +1104,19 @@ ENTRY(native_iret)
/* rcx: threadinfo. interrupts off. */
ENTRY(retint_kernel)
cmpl $0,PER_CPU_VAR(__preempt_count)
- jnz retint_restore_args
+ jz check_int_off
+
+ # atleast preempt count == 0 ?
+ cmpl $_TIF_NEED_RESCHED,PER_CPU_VAR(__preempt_count)
+ jnz retint_restore_args
+
+ cmpl $0, TI_preempt_lazy_count(%rcx)
+ jnz retint_restore_args
+
+ bt $TIF_NEED_RESCHED_LAZY,TI_flags(%rcx)
+ jnc retint_restore_args
+
+check_int_off:
bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */
jnc retint_restore_args
call preempt_schedule_irq
@@ -1540,7 +1552,7 @@ ENTRY(paranoid_exit)
movq %rsp,%rdi /* &pt_regs */
call sync_regs
movq %rax,%rsp /* switch stack for scheduling */
- testl $_TIF_NEED_RESCHED,%ebx
+ testl $_TIF_NEED_RESCHED_MASK,%ebx
jnz paranoid_schedule
movl %ebx,%edx /* arg3: thread flags */
TRACE_IRQS_ON
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