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kernel/mutex: Fix locking to be SMP-safe

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The mutex locking was written to use k_sched_lock(), which doesn't
work as a synchronization primitive if there is another CPU running
(it prevents the current CPU from preempting the thread, it says
nothing about what the others are doing).

Use the pre-existing spinlock for all synchronization.  One wrinkle is
that the priority code was needing to call z_thread_priority_set(),
which is a rescheduling call that cannot be called with a lock held.
So that got split out with a low level utility that can update the
schedule state but allow the caller to defer yielding until later.

Fixes #17584

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
This commit is contained in:
Andy Ross 2019-08-20 11:21:28 -07:00 • committed by Anas Nashif
commit 6f13980fc7
3 changed files with 28 additions and 14 deletions
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kernel/include/ksched.h
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@ -51,6 +51,7 @@ struct k_thread *z_unpend_first_thread(_wait_q_t *wait_q);
void z_unpend_thread(struct k_thread *thread);
int z_unpend_all(_wait_q_t *wait_q);
void z_thread_priority_set(struct k_thread *thread, int prio);
bool z_set_prio(struct k_thread *thread, int prio);
void *z_get_next_switch_handle(void *interrupted);
struct k_thread *z_find_first_thread_to_unpend(_wait_q_t *wait_q,
struct k_thread *from);