With the introduction of the context switch preempt_count invariant,
and the demise of PREEMPT_ACTIVE, its pointless to save/restore the
per-cpu preemption count, it must always be 2.
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
arch/x86/include/asm/preempt.h | 6 +-----
arch/x86/include/asm/thread_info.h | 2 --
arch/x86/kernel/process_32.c | 8 --------
arch/x86/kernel/process_64.c | 8 --------
4 files changed, 1 insertion(+), 23 deletions(-)
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -30,13 +30,9 @@ static __always_inline void preempt_coun
/*
* must be macros to avoid header recursion hell
*/
-#define init_task_preempt_count(p) do { \
- task_thread_info(p)->saved_preempt_count = \
- 2*PREEMPT_DISABLE_OFFSET + PREEMPT_NEED_RESCHED; \
-} while (0)
+#define init_task_preempt_count(p) do { } while (0)
#define init_idle_preempt_count(p, cpu) do { \
- task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
} while (0)
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -57,7 +57,6 @@ struct thread_info {
__u32 flags; /* low level flags */
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
- int saved_preempt_count;
mm_segment_t addr_limit;
void __user *sysenter_return;
unsigned int sig_on_uaccess_error:1;
@@ -69,7 +68,6 @@ struct thread_info {
.task = &tsk, \
.flags = 0, \
.cpu = 0, \
- .saved_preempt_count = INIT_PREEMPT_COUNT, \
.addr_limit = KERNEL_DS, \
}
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -280,14 +280,6 @@ __switch_to(struct task_struct *prev_p,
set_iopl_mask(next->iopl);
/*
- * If it were not for PREEMPT_ACTIVE we could guarantee that the
- * preempt_count of all tasks was equal here and this would not be
- * needed.
- */
- task_thread_info(prev_p)->saved_preempt_count =
this_cpu_read(__preempt_count);
- this_cpu_write(__preempt_count,
task_thread_info(next_p)->saved_preempt_count);
-
- /*
* Now maybe handle debug registers and/or IO bitmaps
*/
if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -401,14 +401,6 @@ __switch_to(struct task_struct *prev_p,
*/
this_cpu_write(current_task, next_p);
- /*
- * If it were not for PREEMPT_ACTIVE we could guarantee that the
- * preempt_count of all tasks was equal here and this would not be
- * needed.
- */
- task_thread_info(prev_p)->saved_preempt_count =
this_cpu_read(__preempt_count);
- this_cpu_write(__preempt_count,
task_thread_info(next_p)->saved_preempt_count);
-
/* Reload esp0 and ss1. This changes current_thread_info(). */
load_sp0(tss, next);
--
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