mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-15 11:56:45 +07:00
d6f029130f
Currently a simple
void foo(void) { preempt_enable(); }
produces the following code on ARM:
foo:
bic r3, sp, #8128
bic r3, r3, #63
ldr r2, [r3, #4]
ldr r1, [r3, #0]
sub r2, r2, #1
tst r1, #4
str r2, [r3, #4]
blne preempt_schedule
mov pc, lr
The problem is that the TIF_NEED_RESCHED flag is loaded _before_ the
preemption count is stored back, hence any interrupt coming within that
3 instruction window causing TIF_NEED_RESCHED to be set won't be
seen and scheduling won't happen as it should.
Nothing currently prevents gcc from performing that reordering. There
is already a barrier() before the decrement of the preemption count, but
another one is needed between this and the TIF_NEED_RESCHED flag test
for proper code ordering.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
65 lines
1.4 KiB
C
65 lines
1.4 KiB
C
#ifndef __LINUX_PREEMPT_H
|
|
#define __LINUX_PREEMPT_H
|
|
|
|
/*
|
|
* include/linux/preempt.h - macros for accessing and manipulating
|
|
* preempt_count (used for kernel preemption, interrupt count, etc.)
|
|
*/
|
|
|
|
#include <linux/config.h>
|
|
#include <linux/thread_info.h>
|
|
#include <linux/linkage.h>
|
|
|
|
#ifdef CONFIG_DEBUG_PREEMPT
|
|
extern void fastcall add_preempt_count(int val);
|
|
extern void fastcall sub_preempt_count(int val);
|
|
#else
|
|
# define add_preempt_count(val) do { preempt_count() += (val); } while (0)
|
|
# define sub_preempt_count(val) do { preempt_count() -= (val); } while (0)
|
|
#endif
|
|
|
|
#define inc_preempt_count() add_preempt_count(1)
|
|
#define dec_preempt_count() sub_preempt_count(1)
|
|
|
|
#define preempt_count() (current_thread_info()->preempt_count)
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
|
|
asmlinkage void preempt_schedule(void);
|
|
|
|
#define preempt_disable() \
|
|
do { \
|
|
inc_preempt_count(); \
|
|
barrier(); \
|
|
} while (0)
|
|
|
|
#define preempt_enable_no_resched() \
|
|
do { \
|
|
barrier(); \
|
|
dec_preempt_count(); \
|
|
} while (0)
|
|
|
|
#define preempt_check_resched() \
|
|
do { \
|
|
if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
|
|
preempt_schedule(); \
|
|
} while (0)
|
|
|
|
#define preempt_enable() \
|
|
do { \
|
|
preempt_enable_no_resched(); \
|
|
barrier(); \
|
|
preempt_check_resched(); \
|
|
} while (0)
|
|
|
|
#else
|
|
|
|
#define preempt_disable() do { } while (0)
|
|
#define preempt_enable_no_resched() do { } while (0)
|
|
#define preempt_enable() do { } while (0)
|
|
#define preempt_check_resched() do { } while (0)
|
|
|
|
#endif
|
|
|
|
#endif /* __LINUX_PREEMPT_H */
|