Fix stack-overflow in scheduler#3
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avsm merged 1 commit intoocaml-multicore:mainfrom Mar 11, 2021
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There's no need to call the scheduler again manually after `continue`. The coroutine will return to the scheduler anyway when done.
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@avsm : I'm not entirely sure how this is supposed to work. Does this look right to you? |
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This looks right; I'd planned to make complete_rw_req and the schedule function mutually recursive anyway, since there needs to be a direct control flow line back to the scheduler in this case. We could do with a test case that spawns a few billion fibres to test the stack safety... |
talex5
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Mar 12, 2021
Before, the continuations all returned `unit`. This makes it easy to get confused about what it means (as in ocaml-multicore#1 and ocaml-multicore#3). Using a distinct type for this should prevent such errors in future. The error in ocaml-multicore#1 now results in: Error: This expression has type effect but an expression was expected of type [ `Exit_scheduler ] The error in ocaml-multicore#3 now results in: Error: This expression has type [ `Exit_scheduler ] but an expression was expected of type unit because it is in the left-hand side of a sequence
talex5
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Nov 11, 2021
Before, the continuations all returned `unit`. This makes it easy to get confused about what it means (as in ocaml-multicore#1 and ocaml-multicore#3). Using a distinct type for this should prevent such errors in future. The error in ocaml-multicore#1 now results in: Error: This expression has type effect but an expression was expected of type [ `Exit_scheduler ] The error in ocaml-multicore#3 now results in: Error: This expression has type [ `Exit_scheduler ] but an expression was expected of type unit because it is in the left-hand side of a sequence
talex5
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Jul 27, 2023
The `execve` action allocated the arrays in the forked child process.
However, in a multi-threaded program we might have forked while another
thread had the malloc lock. In that case, the child would wait forever
because it inherited the locked mutex but not the thread that would
unlock it. e.g.
#0 futex_wait (private=0, expected=2, futex_word=0xffff9509cb10 <main_arena>) at ../sysdeps/nptl/futex-internal.h:146
ocaml-multicore#1 __GI___lll_lock_wait_private (futex=futex@entry=0xffff9509cb10 <main_arena>) at ./nptl/lowlevellock.c:34
ocaml-multicore#2 0x0000ffff94f8e780 in __libc_calloc (n=<optimized out>, elem_size=<optimized out>) at ./malloc/malloc.c:3650
ocaml-multicore#3 0x0000aaaac67cfa68 in make_string_array (errors=errors@entry=37, v_array=281472912006504) at fork_action.c:47
ocaml-multicore#4 0x0000aaaac67cfaf4 in action_execve (errors=37, v_config=281472912003024) at fork_action.c:61
ocaml-multicore#5 0x0000aaaac67cf93c in eio_unix_run_fork_actions (errors=errors@entry=37, v_actions=281472912002960) at fork_action.c:19
talex5
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Jul 28, 2023
The `execve` action allocated the arrays in the forked child process.
However, in a multi-threaded program we might have forked while another
thread had the malloc lock. In that case, the child would wait forever
because it inherited the locked mutex but not the thread that would
unlock it. e.g.
#0 futex_wait (private=0, expected=2, futex_word=0xffff9509cb10 <main_arena>) at ../sysdeps/nptl/futex-internal.h:146
ocaml-multicore#1 __GI___lll_lock_wait_private (futex=futex@entry=0xffff9509cb10 <main_arena>) at ./nptl/lowlevellock.c:34
ocaml-multicore#2 0x0000ffff94f8e780 in __libc_calloc (n=<optimized out>, elem_size=<optimized out>) at ./malloc/malloc.c:3650
ocaml-multicore#3 0x0000aaaac67cfa68 in make_string_array (errors=errors@entry=37, v_array=281472912006504) at fork_action.c:47
ocaml-multicore#4 0x0000aaaac67cfaf4 in action_execve (errors=37, v_config=281472912003024) at fork_action.c:61
ocaml-multicore#5 0x0000aaaac67cf93c in eio_unix_run_fork_actions (errors=errors@entry=37, v_actions=281472912002960) at fork_action.c:19
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There's no need to call the scheduler again manually after
continue. The coroutine will return to the scheduler anyway when done.