void bakery_lock_release(unsigned long mpidr, bakery_lock * bakery)
{
unsigned int entry = platform_get_core_pos(mpidr);
assert_bakery_entry_valid(entry, bakery);
assert(bakery->owner == entry);
bakery->owner = NO_OWNER;
bakery->number[entry] = 0;
}
/*
* 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;
}
/* Release the lock and signal contenders */
void bakery_lock_release(unsigned long mpidr, bakery_lock_t *bakery)
{
unsigned int me = platform_get_core_pos(mpidr);
assert_bakery_entry_valid(me, bakery);
assert(bakery->owner == me);
/*
* Release lock by resetting ownership and ticket. Then signal other
* waiting contenders
*/
bakery->owner = NO_OWNER;
bakery->number[me] = 0;
sev();
}
/* Release the lock and signal contenders */
void bakery_lock_release(bakery_lock_t *bakery)
{
unsigned int me = plat_my_core_pos();
assert_bakery_entry_valid(me, bakery);
assert(bakery_ticket_number(bakery->lock_data[me]));
/*
* Release lock by resetting ticket. Then signal other
* waiting contenders
*/
bakery->lock_data[me] = 0;
dsb();
sev();
}
void bakery_lock_get(unsigned long mpidr, bakery_lock * bakery)
{
unsigned int i, max = 0, my_full_number, his_full_number, entry;
entry = platform_get_core_pos(mpidr);
assert_bakery_entry_valid(entry, bakery);
// Catch recursive attempts to take the lock under the same entry:
assert(bakery->owner != entry);
// Get a ticket
bakery->entering[entry] = 1;
for (i = 0; i < BAKERY_LOCK_MAX_CPUS; ++i) {
if (bakery->number[i] > max) {
max = bakery->number[i];
}
}
++max;
bakery->number[entry] = max;
bakery->entering[entry] = 0;
// Wait for our turn
my_full_number = (max << 8) + entry;
for (i = 0; i < BAKERY_LOCK_MAX_CPUS; ++i) {
while (bakery->entering[i]) ; /* Wait */
do {
his_full_number = bakery->number[i];
if (his_full_number) {
his_full_number = (his_full_number << 8) + i;
}
}
while (his_full_number && (his_full_number < my_full_number));
}
bakery->owner = entry;
}
