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On Mon, 19 Aug 2002, Dave McCracken wrote: > In looking at the code I was wondering something. What happens to the > real parent of a ptraced task when it calls wait4()? If that's its only > child, won't it return ECHILD? yes, this is ugly beyond belief. eg. under bash start up some code that blocks, eg: # cat the shell will not display a prompt, it wait4()s for the 'cat' process to exit. strace the bash PID - it shows the wait4(). strace 'cat' PID (via strace -p) and keep the strace running - it will show 'cat' blocked on console input. [some signal like this could happen to a shell anyway, in a reasonably complex script.] now do something that breaks bash out of its wait4 - eg. send a 'kill -SIGCONT BASH_PID' signal - bash returns with a prompt! The 'cat' becomes a 'background' task - and it gets majorly confused when doing the next shell command in bash - it displays "cat: -: Input/output error" and goes zombie. ptrace is clearly broken - and i tested this with a stock 2.4 kernel. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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