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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
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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