Add missing barriers to Bakery Locks
With the current implementation, it's possible for a contender to observe accesses in the Critical Section before acquiring or releasing the lock. Insert fencing in the locking and release codes to prevent any reorder. Fixes ARM-software/tf-issues#609 Change-Id: I773b82aa41dd544a2d3dbacb9a4b42c9eb767bbb Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
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@ -1,5 +1,5 @@
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/*
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/*
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* Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
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* Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
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*
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*
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* SPDX-License-Identifier: BSD-3-Clause
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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*/
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@ -133,7 +133,12 @@ void bakery_lock_get(bakery_lock_t *bakery)
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bakery_ticket_number(bakery->lock_data[they]));
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bakery_ticket_number(bakery->lock_data[they]));
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}
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}
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}
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}
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/* Lock acquired */
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/*
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* Lock acquired. Ensure that any reads from a shared resource in the
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* critical section read values after the lock is acquired.
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*/
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dmbld();
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}
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}
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@ -146,9 +151,11 @@ void bakery_lock_release(bakery_lock_t *bakery)
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assert(bakery_ticket_number(bakery->lock_data[me]));
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assert(bakery_ticket_number(bakery->lock_data[me]));
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/*
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/*
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* Release lock by resetting ticket. Then signal other
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* Ensure that other observers see any stores in the critical section
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* waiting contenders
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* before releasing the lock. Release the lock by resetting ticket.
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* Then signal other waiting contenders.
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*/
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*/
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dmbst();
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bakery->lock_data[me] = 0;
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bakery->lock_data[me] = 0;
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dsb();
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dsb();
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sev();
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sev();
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@ -204,7 +204,12 @@ void bakery_lock_get(bakery_lock_t *lock)
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== bakery_ticket_number(their_bakery_info->lock_data));
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== bakery_ticket_number(their_bakery_info->lock_data));
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}
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}
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}
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}
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/* Lock acquired */
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/*
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* Lock acquired. Ensure that any reads from a shared resource in the
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* critical section read values after the lock is acquired.
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*/
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dmbld();
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}
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}
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void bakery_lock_release(bakery_lock_t *lock)
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void bakery_lock_release(bakery_lock_t *lock)
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@ -220,6 +225,12 @@ void bakery_lock_release(bakery_lock_t *lock)
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assert(is_lock_acquired(my_bakery_info, is_cached));
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assert(is_lock_acquired(my_bakery_info, is_cached));
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/*
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* Ensure that other observers see any stores in the critical section
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* before releasing the lock. Release the lock by resetting ticket.
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* Then signal other waiting contenders.
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*/
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dmbst();
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my_bakery_info->lock_data = 0;
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my_bakery_info->lock_data = 0;
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write_cache_op(my_bakery_info, is_cached);
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write_cache_op(my_bakery_info, is_cached);
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sev();
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sev();
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