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; }