Use separate type for exiting the scheduler #4
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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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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
added a commit
to talex5/eio
that referenced
this pull request
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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Before, the continuations all returned
unit. This makes it easy to get confused about what it means (as in #1 and #3). Using a distinct type for this should prevent such errors in future.The error in #1 now results in:
The error in #3 now results in: