panic: sx_xlock() of destroyed sx @ /syzkaller/managers/i386/kernel/sys/kern/uipc_sockbuf.c:282
cpuid = 1
time = 1559700020
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe0020ed64e0
vpanic() at vpanic+0x1e0/frame 0xfffffe0020ed6540
panic() at panic+0x43/frame 0xfffffe0020ed65a0
_sx_xlock() at _sx_xlock+0x1c9/frame 0xfffffe0020ed65f0
sblock() at sblock+0xeb/frame 0xfffffe0020ed6620
vn_sendfile() at vn_sendfile+0x650/frame 0xfffffe0020ed68d0
freebsd32_do_sendfile() at freebsd32_do_sendfile+0x195/frame 0xfffffe0020ed6970
ia32_syscall() at ia32_syscall+0x452/frame 0xfffffe0020ed6ab0
int0x80_syscall_common() at int0x80_syscall_common+0x9c/frame 0x8142ea9
KDB: enter: panic
[ thread pid 865 tid 100157 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why