void bakery_lock_get(unsigned int id, unsigned int offset)
{
unsigned int they, me, is_cached;
unsigned int my_ticket, my_prio, their_ticket;
bakery_info_t *their_bakery_info;
unsigned int their_bakery_data;
me = plat_my_core_pos();
is_cached = read_sctlr_el3() & SCTLR_C_BIT;
/* Get a ticket */
my_ticket = bakery_get_ticket(id, offset, me, is_cached);
/*
* Now that we got our ticket, compute our priority value, then compare
* with that of others, and proceed to acquire the lock
*/
my_prio = PRIORITY(my_ticket, me);
for (they = 0; they < BAKERY_LOCK_MAX_CPUS; they++) {
if (me == they)
continue;
/*
* Get a reference to the other contender's bakery info and
* ensure that a stale copy is not read.
*/
their_bakery_info = get_bakery_info_by_index(offset, id, they);
assert(their_bakery_info);
/* Wait for the contender to get their ticket */
do {
read_cache_op(their_bakery_info, is_cached);
their_bakery_data = their_bakery_info->lock_data;
} while (bakery_is_choosing(their_bakery_data));
/*
* If the other party is a contender, they'll have non-zero
* (valid) ticket value. If they do, compare priorities
*/
their_ticket = bakery_ticket_number(their_bakery_data);
if (their_ticket && (PRIORITY(their_ticket, they) < my_prio)) {
/*
* They have higher priority (lower value). Wait for
* their ticket value to change (either release the lock
* to have it dropped to 0; or drop and probably content
* again for the same lock to have an even higher value)
*/
do {
wfe();
read_cache_op(their_bakery_info, is_cached);
} while (their_ticket
== bakery_ticket_number(their_bakery_info->lock_data));
}
}
/* Lock acquired */
}
/*
* Acquire bakery lock
*
* Contending CPUs need first obtain a non-zero ticket and then calculate
* priority value. A contending CPU iterate over all other CPUs in the platform,
* which may be contending for the same lock, in the order of their ordinal
* position (CPU0, CPU1 and so on). A non-contending CPU will have its ticket
* (and priority) value as 0. The contending CPU compares its priority with that
* of others'. The CPU with the highest priority (lowest numerical value)
* acquires the lock
*/
void bakery_lock_get(unsigned long mpidr, bakery_lock_t *bakery)
{
unsigned int they, me;
unsigned int my_ticket, my_prio, their_ticket;
me = platform_get_core_pos(mpidr);
assert_bakery_entry_valid(me, bakery);
/* Prevent recursive acquisition */
assert(bakery->owner != me);
/* Get a ticket */
my_ticket = bakery_get_ticket(bakery, me);
/*
* Now that we got our ticket, compute our priority value, then compare
* with that of others, and proceed to acquire the lock
*/
my_prio = PRIORITY(my_ticket, me);
for (they = 0; they < BAKERY_LOCK_MAX_CPUS; they++) {
if (me == they)
continue;
/* Wait for the contender to get their ticket */
while (bakery->entering[they])
wfe();
/*
* If the other party is a contender, they'll have non-zero
* (valid) ticket value. If they do, compare priorities
*/
their_ticket = bakery->number[they];
if (their_ticket && (PRIORITY(their_ticket, they) < my_prio)) {
/*
* They have higher priority (lower value). Wait for
* their ticket value to change (either release the lock
* to have it dropped to 0; or drop and probably content
* again for the same lock to have an even higher value)
*/
do {
wfe();
} while (their_ticket == bakery->number[they]);
}
}
/* Lock acquired */
bakery->owner = me;
}
