On 22 May 2017 at 19:43, Denys Vlasenko <vda.li...@googlemail.com> wrote: >> I am not sure what is the right place to fix this. Any comment on this? >> For me it works to suppress this signal on the corresponding poll() call. > > Well, SIGCHLD may have a trap, so, that would not be correct. > > Fixed in git, please try. Thanks for your fix. Works perfect for my script (controlling a cellular modem)
I was curious how to catch SIGCHLD using trap and what behavior we should expect. Could you also provide a test for trap in conjunction with SIGCHLD. Here my tries with results from busybox-git with your fix: # sleep 1& read x => no trap signal handler installed, read waits now forever for input # trap "echo --TRAP---" CHLD; sleep 1& read x --TRAP--- [1]+ Done sleep 1 => Okay, read will be interrupted after one second (this works now thanks your fixes in signal handling coder. It would not work correctly in busybox 1.24 versions) # sleep 1& read x --TRAP--- [1]+ Done sleep 1 => Okay, trap handler still installed, same in subsequent commands # trap '' CHLD # sleep 1& read x [1]+ Done sleep 1 => Is this correct? Set SIGCHLD to ignore, read still will be interrupted after one second. # trap - CHLD # sleep 1& read x => Okay, set SIGCHLD to default. read now waits for ever again.
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