I didn't like ithe "SIGKILL operates similarly, with exceptions" phrase (if it's different, then it's not "similar", right?), and now I got around to changing it. Now it says simply: "SIGKILL does not generate signal-delivery-stop and therefore the tracer can't suppress it." Replaced "why WNOHANG is not reliable" example with a more realistic one (the one which actually inspired to add this information to man page in the first place): we got ESRCH - process is gone! - but waitpid(WNOHANG) can still confusingly return 0 "no processes to wait for". Replaced "This means that unneeded trailing arguments may be omitted" part with a much better recommendation to never do that and to supply zero arguments instead. (The part about "undocumentedness" of gcc behavior was bogus, btw - deleted). Expanded BUGS section with the explanation and an example of visible strace behavior on the buggy syscalls which exit with EINTR on ptrace attach. I hope this will lead to people submitting better bug reports to lkml about such syscalls. Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>