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https://github.com/rd-stuffs/msm-4.14.git
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87f2c340bb
Currently, thread flag tests are unordered with respect to flag changes, which results in thread flag changes not becoming immediately visible to other CPUs. On a weakly-ordered CPU, this is most noticeable with the TIF_NEED_RESCHED flag and optimistic lock spinners, where the preemptoff tracer shows an optimistic lock spinner will often elapse its scheduling quantum despite checking TIF_NEED_RESCHED on every loop iteration. This leads to scheduling delays and latency spikes, especially when disabling preemption is involved, as is the case for optimistic lock spinning. Making the thread flag helpers ordered with respect to test operations resolves the issue seen in the preemptoff tracer. Now, optimistic lock spinners bail out in a timely manner, and other TIF_NEED_RESCHED users will benefit similarly. Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> Signed-off-by: azrim <mirzaspc@gmail.com>
196 lines
5.0 KiB
C
196 lines
5.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* thread_info.h: common low-level thread information accessors
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*
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* Copyright (C) 2002 David Howells (dhowells@redhat.com)
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* - Incorporating suggestions made by Linus Torvalds
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*/
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#ifndef _LINUX_THREAD_INFO_H
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#define _LINUX_THREAD_INFO_H
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#include <linux/types.h>
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#include <linux/bug.h>
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#include <linux/restart_block.h>
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#include <linux/errno.h>
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#ifdef CONFIG_THREAD_INFO_IN_TASK
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/*
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* For CONFIG_THREAD_INFO_IN_TASK kernels we need <asm/current.h> for the
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* definition of current, but for !CONFIG_THREAD_INFO_IN_TASK kernels,
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* including <asm/current.h> can cause a circular dependency on some platforms.
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*/
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#include <asm/current.h>
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#define current_thread_info() ((struct thread_info *)current)
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#endif
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#include <linux/bitops.h>
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/*
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* For per-arch arch_within_stack_frames() implementations, defined in
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* asm/thread_info.h.
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*/
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enum {
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BAD_STACK = -1,
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NOT_STACK = 0,
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GOOD_FRAME,
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GOOD_STACK,
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};
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#include <asm/thread_info.h>
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#ifdef __KERNEL__
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#ifndef arch_set_restart_data
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#define arch_set_restart_data(restart) do { } while (0)
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#endif
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static inline long set_restart_fn(struct restart_block *restart,
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long (*fn)(struct restart_block *))
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{
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restart->fn = fn;
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arch_set_restart_data(restart);
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return -ERESTART_RESTARTBLOCK;
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}
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#ifndef THREAD_ALIGN
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#define THREAD_ALIGN THREAD_SIZE
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#endif
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#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO)
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/*
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* flag set/clear/test wrappers
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* - pass TIF_xxxx constants to these functions
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*/
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static inline void set_ti_thread_flag(struct thread_info *ti, int flag)
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{
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/* set_bit() with release semantics */
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smp_mb__before_atomic();
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set_bit(flag, (unsigned long *)&ti->flags);
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}
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static inline void clear_ti_thread_flag(struct thread_info *ti, int flag)
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{
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/* clear_bit() with release semantics */
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smp_mb__before_atomic();
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clear_bit(flag, (unsigned long *)&ti->flags);
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}
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static inline void update_ti_thread_flag(struct thread_info *ti, int flag,
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bool value)
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{
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if (value)
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set_ti_thread_flag(ti, flag);
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else
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clear_ti_thread_flag(ti, flag);
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}
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static inline int test_and_set_ti_thread_flag(struct thread_info *ti, int flag)
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{
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atomic_long_t *p = (atomic_long_t *)&ti->flags;
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const unsigned long mask = BIT_MASK(flag);
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long old;
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/* test_and_set_bit() sans the unordered test */
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p += BIT_WORD(flag);
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old = atomic_long_fetch_or(mask, p);
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return !!(old & mask);
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}
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static inline int test_and_clear_ti_thread_flag(struct thread_info *ti, int flag)
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{
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atomic_long_t *p = (atomic_long_t *)&ti->flags;
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const unsigned long mask = BIT_MASK(flag);
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long old;
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/* test_and_clear_bit() sans the unordered test */
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p += BIT_WORD(flag);
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old = atomic_long_fetch_andnot(mask, p);
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return !!(old & mask);
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}
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static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
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{
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const atomic_long_t *p = (atomic_long_t *)&ti->flags;
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/* test_bit() with acquire semantics */
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p += BIT_WORD(flag);
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return !!(atomic_long_read_acquire(p) & BIT_MASK(flag));
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}
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#define set_thread_flag(flag) \
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set_ti_thread_flag(current_thread_info(), flag)
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#define clear_thread_flag(flag) \
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clear_ti_thread_flag(current_thread_info(), flag)
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#define update_thread_flag(flag, value) \
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update_ti_thread_flag(current_thread_info(), flag, value)
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#define test_and_set_thread_flag(flag) \
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test_and_set_ti_thread_flag(current_thread_info(), flag)
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#define test_and_clear_thread_flag(flag) \
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test_and_clear_ti_thread_flag(current_thread_info(), flag)
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#define test_thread_flag(flag) \
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test_ti_thread_flag(current_thread_info(), flag)
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#define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
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#ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
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static inline int arch_within_stack_frames(const void * const stack,
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const void * const stackend,
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const void *obj, unsigned long len)
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{
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return 0;
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}
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#endif
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#ifdef CONFIG_HARDENED_USERCOPY
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extern void __check_object_size(const void *ptr, unsigned long n,
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bool to_user);
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static __always_inline void check_object_size(const void *ptr, unsigned long n,
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bool to_user)
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{
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if (!__builtin_constant_p(n))
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__check_object_size(ptr, n, to_user);
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}
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#else
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static inline void check_object_size(const void *ptr, unsigned long n,
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bool to_user)
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{ }
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#endif /* CONFIG_HARDENED_USERCOPY */
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extern void __compiletime_error("copy source size is too small")
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__bad_copy_from(void);
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extern void __compiletime_error("copy destination size is too small")
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__bad_copy_to(void);
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static inline void copy_overflow(int size, unsigned long count)
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{
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WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
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}
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static __always_inline bool
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check_copy_size(const void *addr, size_t bytes, bool is_source)
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{
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int sz = __compiletime_object_size(addr);
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if (unlikely(sz >= 0 && sz < bytes)) {
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if (!__builtin_constant_p(bytes))
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copy_overflow(sz, bytes);
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else if (is_source)
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__bad_copy_from();
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else
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__bad_copy_to();
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return false;
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}
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check_object_size(addr, bytes, is_source);
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return true;
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}
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#ifndef arch_setup_new_exec
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static inline void arch_setup_new_exec(void) { }
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#endif
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#endif /* __KERNEL__ */
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#endif /* _LINUX_THREAD_INFO_H */
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