Fix the logic for scanning tasks in the Julia GC #4053
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This removes an unnecessary (and wrong) test that intended to avoid repeated scanning of the main thread stack, but instead skipped scanning of all root stacks.
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fingolfin
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Jun 17, 2020
| @@ -646,7 +646,7 @@ static void GapTaskScanner(jl_task_t * task, int root_task) | |||
| if (tag->bits.gc & 2) | |||
| rescan = 0; | |||
| } | |||
| if (stack && tid < 0) { | |||
| if (stack) { | |||
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This seems like the right thing to do....
In fact tid < 0 means tid == -1 means that the task is not the current task of any thread. Why was it ever OK to skip scanning the stack of such tasks? It might have been the previously active task on a thread, right? And then skipping it could lead to us missing a GC root and hence a GC crash, no?
Or is it not that bad? Then what am I missing this time?
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You aren't missing anything, that was a bug.
fingolfin
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Backported to stable-4.11 in 1450c23 |
PaulaHaehndel
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PaulaHaehndel
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fingolfin
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kind: bug: crash
ThomasBreuer
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Feb 24, 2021
- gap-system#3925 belongs to 4.12.0 not 4.11.1, - gap-system#4053 now belongs to `topic: julia`, not to `kind: bug: crash` - removed a superfluous "in"
ThomasBreuer
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Feb 25, 2021
- gap-system#3925 belongs to 4.12.0 not 4.11.1, - gap-system#4053 now belongs to `topic: julia`, not to `kind: bug: crash` - removed a superfluous "in"
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This fixes the test that tries to avoid scanning the stack of the current thread twice.