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Linked failure: add ASCII art. Close #1868.

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This commit is contained in:
Ben Blum 2012-08-01 23:01:50 -04:00
parent 7cb3f3e86a
commit ac0c8b0823
1 changed files with 59 additions and 5 deletions
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64
src/libcore/task.rs
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@ -585,11 +585,67 @@ unsafe fn atomically<U>(f: fn() -> U) -> U {
}
/****************************************************************************
* Internal
* Spawning & linked failure
*
* Several data structures are involved in task management to allow properly
* propagating failure across linked/supervised tasks.
*
* (1) The "taskgroup_arc" is an arc::exclusive which contains a hashset of
* all tasks that are part of the group. Some tasks are 'members', which
* means if they fail, they will kill everybody else in the taskgroup.
* Other tasks are 'descendants', which means they will not kill tasks
* from this group, but can be killed by failing members.
*
* A new one of these is created each spawn_linked or spawn_supervised.
*
* (2) The "taskgroup" is a per-task control structure that tracks a task's
* spawn configuration. It contains a reference to its taskgroup_arc,
* a reference to its node in the ancestor list (below), a flag for
* whether it's part of the 'main'/'root' taskgroup, and an optionally
* configured notification port. These are stored in TLS.
*
* (3) The "ancestor_list" is a cons-style list of arc::exclusives which
* tracks 'generations' of taskgroups -- a group's ancestors are groups
* which (directly or transitively) spawn_supervised-ed them. Each task
* recorded in the 'descendants' of each of its ancestor groups.
*
* Spawning a supervised task is O(n) in the number of generations still
* alive, and exiting (by success or failure) that task is also O(n).
*
* This diagram depicts the references between these data structures:
*
* linked_________________________________
* ___/ _________ \___
* / \ | group X | / \
* ( A ) - - - - - - - > | {A,B} {}|< - - -( B )
* \___/ |_________| \___/
* unlinked
* | __ (nil)
* | //| The following code causes this:
* |__ // /\ _________
* / \ // || | group Y | fn taskA() {
* ( C )- - - ||- - - > |{C} {D,E}| spawn(taskB);
* \___/ / \=====> |_________| spawn_unlinked(taskC);
* supervise /gen \ ...
* | __ \ 00 / }
* | //| \__/ fn taskB() { ... }
* |__ // /\ _________ fn taskC() {
* / \/ || | group Z | spawn_supervised(taskD);
* ( D )- - - ||- - - > | {D} {E} | ...
* \___/ / \=====> |_________| }
* supervise /gen \ fn taskD() {
* | __ \ 01 / spawn_supervised(taskE);
* | //| \__/ ...
* |__ // _________ }
* / \/ | group W | fn taskE() { ... }
* ( E )- - - - - - - > | {E} {} |
* \___/ |_________|
*
* "taskgroup" "taskgroup_arc"
* "ancestor_list"
*
****************************************************************************/
/* spawning */
type sched_id = int;
type task_id = int;
@ -598,8 +654,6 @@ unsafe fn atomically<U>(f: fn() -> U) -> U {
type rust_task = libc::c_void;
type rust_closure = libc::c_void;
/* linked failure */
type taskset = send_map::linear::linear_map<*rust_task,()>;
fn new_taskset() -> taskset {