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lib/thread: Add mutex 

We need a way to protect shared resources. Since we are using
cooperative multitasking the mutex implementation is pretty trivial.

BUG=b:179699789
TEST=Verify thread lock and unlock.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ife1ac95ec064ebcdd00fcaacec37a06ac52885ff
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56230
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
This commit is contained in:
Raul E Rangel 2021-07-12 13:49:59 -06:00 committed by Raul Rangel
parent a98d302fe9
commit b29f9d471b
2 changed files with 31 additions and 0 deletions
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11
src/include/thread.h
View File

@ -6,6 +6,10 @@
#include <bootstate.h>
#include <arch/cpu.h>
struct thread_mutex {
bool locked;
};
#if ENV_RAMSTAGE && CONFIG(COOP_MULTITASKING)
struct thread {
@ -53,6 +57,9 @@ int thread_yield_microseconds(unsigned int microsecs);
void thread_coop_enable(void);
void thread_coop_disable(void);
void thread_mutex_lock(struct thread_mutex *mutex);
void thread_mutex_unlock(struct thread_mutex *mutex);
static inline void thread_init_cpu_info_non_bsp(struct cpu_info *ci)
{
ci->thread = NULL;
@ -85,6 +92,10 @@ static inline void thread_coop_enable(void) {}
static inline void thread_coop_disable(void) {}
struct cpu_info;
static inline void thread_init_cpu_info_non_bsp(struct cpu_info *ci) { }
static inline void thread_mutex_lock(struct thread_mutex *mutex) {}
static inline void thread_mutex_unlock(struct thread_mutex *mutex) {}
#endif
#endif /* THREAD_H_ */

20
src/lib/thread.c
View File

@ -1,5 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0-only */
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
@ -377,3 +378,22 @@ void thread_coop_disable(void)
current->can_yield--;
}
void thread_mutex_lock(struct thread_mutex *mutex)
{
struct stopwatch sw;
stopwatch_init(&sw);
while (mutex->locked)
assert(thread_yield() == 0);
mutex->locked = true;
printk(BIOS_SPEW, "took %lu us to acquire mutex\n", stopwatch_duration_usecs(&sw));
}
void thread_mutex_unlock(struct thread_mutex *mutex)
{
assert(mutex->locked);
mutex->locked = 0;
}