Commit-ID: d87b7a33794f52226131f93cbc9db03274d9fecf
Gitweb: http://git.kernel.org/tip/d87b7a33794f52226131f93cbc9db03274d9fecf
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 28 Sep 2015 18:11:18 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 6 Oct 2015 17:08:18 +0200
sched/core, sched/x86: Kill thread_info::saved_preempt_count
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) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/preempt.h | 5 +----
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(+), 22 deletions(-)
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 01e700d..01bcde8 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -30,12 +30,9 @@ static __always_inline void preempt_count_set(int pc)
/*
* must be macros to avoid header recursion hell
*/
-#define init_task_preempt_count(p) do { \
- task_thread_info(p)->saved_preempt_count = FORK_PREEMPT_COUNT; \
-} 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)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 8afdc3e..809877e 100644
--- 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, \
}
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 737527b..9f95091 100644
--- 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, struct task_struct *next_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 ||
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b35921a..d7f1d5c 100644
--- 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, struct task_struct *next_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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