malloc-deadlock on macOS Big Sur crashes often

[Douglas Katzman]

I see this very frequently now, having upgraded the OS recently:

::: Running (RUN-PROGRAM :MALLOC-DEADLOCK)
.............CORRUPTION WARNING in SBCL pid 70353 pthread 0x700000c1b000:
Memory fault at 0xffffffff992a0c05 (pc=0x529078b3 [code 0x52907320+0x593 ID 0x7c46], fp=0x4d4f928, sp=0x4d4f898) pthread 0x700000c1b000
The integrity of this image is possibly compromised.
Continuing with fingers crossed.
Unhandled SB-SYS:MEMORY-FAULT-ERROR in thread #<SB-THREAD:THREAD RUNNING
                                                 {1001668293}>:
  Unhandled memory fault at #xFFFFFFFF992A0C05.

Backtrace for: #<SB-THREAD:THREAD RUNNING {1001668293}>
0: ((FLET "CLEANUP-FUN-10" :IN SB-KERNEL:SUB-GC)) [cleanup]
1: (SB-KERNEL:SUB-GC 6)
2: (GC :FULL T :GEN 0)
3: ((LAMBDA NIL :IN "/Users/dougk/lisp/sbcl/tests/run-program.impure.lisp"))
4: ((FLET SB-UNIX::BODY :IN SB-THREAD::RUN))
5: ((FLET "WITHOUT-INTERRUPTS-BODY-11" :IN SB-THREAD::RUN))
6: ((FLET SB-UNIX::BODY :IN SB-THREAD::RUN))
7: ((FLET "WITHOUT-INTERRUPTS-BODY-4" :IN SB-THREAD::RUN))
8: (SB-THREAD::RUN)
9: ("foreign function: call_into_lisp")
10: ("foreign function: funcall1")

[Douglas Katzman (dougk)]

This only happens under parallel-exec.sh, and I think Stas demonstrated that it is because fork() not followed by exec() is disallowed when using some Apple synchronization primitives.
Closing as invalid.