diff options
Diffstat (limited to 'patches/x86__Support_for_lazy_preemption.patch')
-rw-r--r-- | patches/x86__Support_for_lazy_preemption.patch | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/patches/x86__Support_for_lazy_preemption.patch b/patches/x86__Support_for_lazy_preemption.patch new file mode 100644 index 000000000000..72c10f11de7d --- /dev/null +++ b/patches/x86__Support_for_lazy_preemption.patch @@ -0,0 +1,155 @@ +Subject: x86: Support for lazy preemption +From: Thomas Gleixner <tglx@linutronix.de> +Date: Thu Nov 1 11:03:47 2012 +0100 + +From: Thomas Gleixner <tglx@linutronix.de> + +Implement the x86 pieces for lazy preempt. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> + + +--- + arch/x86/Kconfig | 1 + + arch/x86/include/asm/preempt.h | 33 ++++++++++++++++++++++++++++++++- + arch/x86/include/asm/thread_info.h | 7 +++++++ + include/linux/entry-common.h | 2 +- + kernel/entry/common.c | 2 +- + 5 files changed, 42 insertions(+), 3 deletions(-) +--- +diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig +index 3dc12f4a730a..34421efd2336 100644 +--- a/arch/x86/Kconfig ++++ b/arch/x86/Kconfig +@@ -230,6 +230,7 @@ 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 f8cb8af4de5c..271b745b879c 100644 +--- a/arch/x86/include/asm/preempt.h ++++ b/arch/x86/include/asm/preempt.h +@@ -90,17 +90,48 @@ 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 de406d93b515..730d86e28f46 100644 +--- a/arch/x86/include/asm/thread_info.h ++++ b/arch/x86/include/asm/thread_info.h +@@ -57,11 +57,14 @@ struct thread_info { + unsigned long flags; /* low level flags */ + unsigned long syscall_work; /* SYSCALL_WORK_ 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__ */ +@@ -90,6 +93,7 @@ struct thread_info { + #define TIF_NOTSC 16 /* TSC is not accessible in userland */ + #define TIF_NOTIFY_SIGNAL 17 /* signal notifications exist */ + #define TIF_SLD 18 /* Restore split lock detection on context switch */ ++#define TIF_NEED_RESCHED_LAZY 19 /* lazy rescheduling necessary */ + #define TIF_MEMDIE 20 /* is terminating due to OOM killer */ + #define TIF_POLLING_NRFLAG 21 /* idle is polling for TIF_NEED_RESCHED */ + #define TIF_IO_BITMAP 22 /* uses I/O bitmap */ +@@ -113,6 +117,7 @@ struct thread_info { + #define _TIF_NOTSC (1 << TIF_NOTSC) + #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) +@@ -143,6 +148,8 @@ 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 2e2b8d6140ed..572fac3dd288 100644 +--- a/include/linux/entry-common.h ++++ b/include/linux/entry-common.h +@@ -59,7 +59,7 @@ + + #define EXIT_TO_USER_MODE_WORK \ + (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ +- _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \ ++ _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 79c7614c975f..d8bedab935b2 100644 +--- a/kernel/entry/common.c ++++ b/kernel/entry/common.c +@@ -159,7 +159,7 @@ 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 |