signals

问题 According to this paragraph ,the following has problem: /* usr_interrupt is set by the signal handler. */ if (!usr_interrupt) pause (); /* Do work once the signal arrives. */ ... And should use sigsuspend instead. But I still don't see what the problem is with pause and how sigsuspend solves it, anyone can explain in more details? 回答1: Let's examine what happens when a signal arrives after you've checked usr_interrupt but before you call pause : main thread signal handler ----------- --------

问题 http://www.masterraghu.com/subjects/np/introduction/unix_network_programming_v1.3/ch13lev1sec4.html (excerpt from Richard Steven's UNIX Network Programming Vol. 1) includes Signal(SIGHUP, SIG_IGN); as part of the daemon_init function because: ..."We must ignore SIGHUP because when the session leader terminates (the first child), all processes in the session (our second child) receive the SIGHUP signal." The core of the function is: int i; pid_t pid; if ( (pid = Fork()) < 0) return (-1); else

问题 I'm trying to write a process in C/linux that ignores the SIGINT and SIGQUIT signals and exits for the SIGTERM. For the other signals it should write out the signal and the time. I'm having trouble cathing all the signals because i'm familiar only with catching 1 signal. If anyone could help me with this I'd appreciate it very much. Here is my code: #include <signal.h> #include <stdio.h> #include <string.h> #include <unistd.h> #include <time.h> int done = 0; void term(int signum) { if (signum

问题 I'm trying to write a process in C/linux that ignores the SIGINT and SIGQUIT signals and exits for the SIGTERM. For the other signals it should write out the signal and the time. I'm having trouble cathing all the signals because i'm familiar only with catching 1 signal. If anyone could help me with this I'd appreciate it very much. Here is my code: #include <signal.h> #include <stdio.h> #include <string.h> #include <unistd.h> #include <time.h> int done = 0; void term(int signum) { if (signum

问题 What is the workflow of processing a signal in python ? I set a signal handler, when the signal occur ,how does python invoke my function? Does the OS invoke it just like C program? If I am in a C extend of python ,is it interrupted immediately ? Now it's clear to me how does python process handle a signal . When you set a signal by the signal module , the module will register a function signal_handler(see $src/Modules/signalmodule.c) ,which set your handler and flag it as 1( Handlers[sig_num

问题 The C89 standard states: At sequence points volatile objects are stable in the sense that previous evaluations are complete and subsequent evaluations have not yet occurred. The C89 standard also states: When the processing of the abstract machine is interrupted by receipt of a signal, only the values of objects as of the previous sequence point may be relied on. These requirements leave me confused, because I can't imagine how they would actually be implemented. I only have a rudimentary

问题 So, I am trying to return from a floating point exception, but my code keeps looping instead. I can actually exit the process, but what I want to do is return and redo the calculation that causes the floating point error. The reason the FPE occurs is because I have a random number generator that generates coefficients for a polynomial. Using some LAPACK functions, I solve for the roots and do some other things. Somewhere in this math intensive chain, a floating point exception occurs. When

问题 So, I am trying to return from a floating point exception, but my code keeps looping instead. I can actually exit the process, but what I want to do is return and redo the calculation that causes the floating point error. The reason the FPE occurs is because I have a random number generator that generates coefficients for a polynomial. Using some LAPACK functions, I solve for the roots and do some other things. Somewhere in this math intensive chain, a floating point exception occurs. When

问题 So, I am trying to return from a floating point exception, but my code keeps looping instead. I can actually exit the process, but what I want to do is return and redo the calculation that causes the floating point error. The reason the FPE occurs is because I have a random number generator that generates coefficients for a polynomial. Using some LAPACK functions, I solve for the roots and do some other things. Somewhere in this math intensive chain, a floating point exception occurs. When

问题 The C89 standard states: At sequence points volatile objects are stable in the sense that previous evaluations are complete and subsequent evaluations have not yet occurred. The C89 standard also states: When the processing of the abstract machine is interrupted by receipt of a signal, only the values of objects as of the previous sequence point may be relied on. These requirements leave me confused, because I can't imagine how they would actually be implemented. I only have a rudimentary