eace1df539
Recent changes post-scheduler-rewrite broke scheduling on SMP: The "preempt_ok" feature added to isolate preemption points wasn't honored in SMP mode. Fix this by adding a "swap_ok" field to the CPU record (not the thread) which is set at the same time out of update_cache(). The "queued" flag wasn't being maintained correctly when swapping away from _current (it was added back to the queue, but the flag wasn't set). Abstract out a "should_preempt()" predicate so SMP and uniprocessor paths share the same logic, which is distressingly subtle. There were two places where _Swap() was predicated on _get_next_ready_thread() != _current. That's no longer a benign optimization in SMP, where the former function REMOVES the next thread from the queue. Just call _Swap() directly in SMP, which has a unified C implementation that does this test already. Don't change other architectures in case it exposes bugs with _Swap() switching back to the same thread (it should work, I just don't want to break anything). Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
97 lines
2.2 KiB
C
97 lines
2.2 KiB
C
/*
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* Copyright (c) 2018 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef _KSWAP_H
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#define _KSWAP_H
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#include <ksched.h>
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#include <kernel_arch_func.h>
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#ifdef CONFIG_TIMESLICING
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extern void _update_time_slice_before_swap(void);
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#else
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#define _update_time_slice_before_swap() /**/
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#endif
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#ifdef CONFIG_STACK_SENTINEL
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extern void _check_stack_sentinel(void);
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#else
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#define _check_stack_sentinel() /**/
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#endif
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extern void _sys_k_event_logger_context_switch(void);
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/* In SMP, the irq_lock() is a spinlock which is implicitly released
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* and reacquired on context switch to preserve the existing
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* semantics. This means that whenever we are about to return to a
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* thread (via either _Swap() or interrupt/exception return!) we need
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* to restore the lock state to whatever the thread's counter
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* expects.
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*/
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void _smp_reacquire_global_lock(struct k_thread *thread);
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void _smp_release_global_lock(struct k_thread *thread);
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/* context switching and scheduling-related routines */
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#ifdef CONFIG_USE_SWITCH
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/* New style context switching. _arch_switch() is a lower level
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* primitive that doesn't know about the scheduler or return value.
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* Needed for SMP, where the scheduler requires spinlocking that we
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* don't want to have to do in per-architecture assembly.
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*/
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static inline unsigned int _Swap(unsigned int key)
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{
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struct k_thread *new_thread, *old_thread;
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int ret = 0;
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old_thread = _current;
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_check_stack_sentinel();
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_update_time_slice_before_swap();
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#ifdef CONFIG_KERNEL_EVENT_LOGGER_CONTEXT_SWITCH
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_sys_k_event_logger_context_switch();
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#endif
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new_thread = _get_next_ready_thread();
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if (new_thread != old_thread) {
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old_thread->swap_retval = -EAGAIN;
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#ifdef CONFIG_SMP
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_current_cpu->swap_ok = 0;
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new_thread->base.cpu = _arch_curr_cpu()->id;
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_smp_release_global_lock(new_thread);
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#endif
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_current = new_thread;
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_arch_switch(new_thread->switch_handle,
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&old_thread->switch_handle);
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ret = _current->swap_retval;
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}
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irq_unlock(key);
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return ret;
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}
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#else /* !CONFIG_USE_SWITCH */
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extern unsigned int __swap(unsigned int key);
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static inline unsigned int _Swap(unsigned int key)
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{
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_check_stack_sentinel();
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_update_time_slice_before_swap();
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return __swap(key);
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}
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#endif
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#endif /* _KSWAP_H */
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