回复：Queries that should be canceled will get stuck on secure_write function

I add a test to reproduce the problem, you can see the attachment for specific content

during the last sleep time of the test, use pstack to get the stack of the backend process, which is as follows:

#0  0x00007f6ebdd744d3 in __epoll_wait_nocancel () from /lib64/libc.so.6
#1  0x00000000007738d2 in WaitEventSetWait ()
#2  0x0000000000675aae in secure_write ()
#3  0x000000000067bfab in internal_flush ()
#4  0x000000000067c13a in internal_putbytes ()
#5  0x000000000067c217 in socket_putmessage ()
#6  0x0000000000497f36 in printtup ()
#7  0x00000000006301e0 in standard_ExecutorRun ()
#8  0x00000000007985fb in PortalRunSelect ()
#9  0x0000000000799968 in PortalRun ()
#10 0x0000000000795866 in exec_simple_query ()
#11 0x0000000000796cff in PostgresMain ()
#12 0x0000000000488339 in ServerLoop ()
#13 0x0000000000717bbc in PostmasterMain ()
#14 0x0000000000488f26 in main ()