Comment 3 for bug 1123267

Maybe the output of strace can help. I attached to the process right after typing ":w" in VIM and then pressed enter to catch less keyboard events:

Process 3304 attached - interrupt to quit
select(1, [0], NULL, [0], NULL) = 1 (in [0])
read(0, "\r", 4096) = 1
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
write(1, "\r", 1) = 1
stat("/home/bikeshedder/x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
access("/home/bikeshedder/x", W_OK) = 0
getcwd("/home/bikeshedder", 4096) = 12
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
write(1, "\33[?25l\"x\"", 9) = 9
stat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
access("x", W_OK) = 0
getxattr("x", "system.posix_acl_access", 0x7fff5cc33380, 132) = -1 ENODATA (No data available)
stat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
lstat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
lstat("4913", 0x7fff5cc33660) = -1 ENOENT (No such file or directory)
open("4913", O_WRONLY|O_CREAT|O_EXCL|O_NOFOLLOW, 0100664) = 3
fchown(3, 1000, 1000) = 0
stat("4913", {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
close(3) = 0
unlink("4913") = 0
stat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
stat("/home/bikeshedder/.vimbackup/x~", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
unlink("/home/bikeshedder/.vimbackup/x~") = 0
rename("x", "/home/bikeshedder/.vimbackup/x~") = 0
fsync(4) = 0
open("x", O_WRONLY|O_CREAT|O_TRUNC, 0664) = 3
write(3, "\n", 1) = 1
fsync(3) = 0
stat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
stat("x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
close(3) = 0
chmod("x", 0100664) = 0
setxattr("x", "system.posix_acl_access", "\x02\x00\x00\x00\x01\x00\x06\x00\xff\xff\xff\xff\x04\x00\x06\x00\xff\xff\xff\xff \x00\x04\x00\xff\xff\xff\xff", 28, 0) = 0
write(1, " 1L, 1C [w]", 11) = 11
stat("/home/bikeshedder/x", {st_mode=S_IFREG|0664, st_size=1, ...}) = 0
getcwd("/home/bikeshedder", 4096) = 12
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
write(1, "\33[1;3H", 6) = 6
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
select(1, [0], NULL, [0], {0, 0}) = 0 (Timeout)
write(1, "\33[?12l\33[?25h", 12) = 12
select(1, [0], NULL, [0], {10, 0}^C <unfinished ...>
Process 3304 detached