A magical BUG occurred when Linux used ITIMER_REAL and ITIMER_VIRTUAL timers at the same time

bqgup

A magical BUG occurred when Linux used ITIMER_REAL and ITIMER_VIRTUAL timers at the same time [Copy link]

 

#A magical BUG occurred when linux used ITIMER_REAL and ITIMER_VIRTUAL timers at the same time ##A brief introduction to Linux timers ITIMER_REAL timer will send a SIGALRM signal every time the timing time comes. When the main function receives this signal, it calls the signal processing function; The usage of ITIMER_VIRTUAL and ITIMER_PROF is similar. When the timer you set in setitimer is ITIMER_VIRTUAL, you change the SIGALRM in sigaction to SIGVTALARM; Similarly, ITIMER_PROF corresponds to SIGPROF; ##The code for using ITIMER_REAL and ITIMER_VIRTUAL timers at the same time in linux is as follows: ```c #include "timer.h" #include<unistd.h> #include<sched.h> #include<time.h> #include<sys time.h=""> #include<signal.h> #include<unistd.h> #include<errno.h> #include<stdio.h> int aaa = 0; int bbb = 0; int ccc = 0; /* Function name: init_time Function: Set timing time*/ void init_timer_real(void) { struct itimerval value; value.it_value.tv_sec = 1;//seconds value.it_value.tv_usec = 0;//Microseconds; value.it_interval = value.it_value; /* set ITIMER_REAL */ setitimer(ITIMER_REAL, &value, NULL); } void shutdown_timer_real(void) { struct itimerval value; value.it_value .tv_sec = 0;//Second value.it_value.tv_usec = 0;//Microsecond; value.it_interval = value.it_value; /* set ITIMER_REAL */ setitimer(ITIMER_REAL, &value, NULL);//Set timer ITIMER_REAL } /* Function name: init_sigaction Function: Specify the timing operation content*/ void init_sigaction_timer_real(void) { struct sigaction tact; tact.sa_handler = timeout_info_timer_real; tact.sa_flags = 0; sigemptyset (&tact. sa_mask); //sigemptyset is used to initialize and clear the parameter set signal set. sigaction(SIGALRM, &tact, NULL);//Establish signal processing mechanism} /* Timer operation*/ /* Function name: timeout_info Function: Timing operation content input: not used*/ void timeout_info_timer_real(int signo)//Timing operation Contents{ static unsigned int two_timer = 2; static unsigned int five_timer = 5; static unsigned int ten_timer = 10; two_timer--; if(0 == two_timer) { two_timer = 2; //Perform some operation} five_timer--; if(0 == five_timer) { five_timer = 5; //Perform some operation} ten_timer--; if(0 == ten_timer) { ten_timer = 10; //Perform some operation} printf("timer = %d\ n",aaa++); } void init_timer_virtual(void) { struct itimerval value; value.it_value.tv_sec = 1;//seconds value.it_value.tv_usec = 0;//microseconds; value.it_interval = value.it_value; /* set ITIMER_REAL */ setitimer(ITIMER_VIRTUAL , &value, NULL); } void shutdown_timer_virtual(void) { struct itimerval value; value.it_value.tv_sec = 0;//seconds value.it_value.tv_usec = 0;//microseconds; value.it_interval = value.it_value; / * set ITIMER_REAL */ setitimer(ITIMER_VIRTUAL, &value, NULL);//Set timer ITIMER_REAL } /* Function name: init_sigaction Function: Specify the timing operation content */ void init_sigaction_timer_virtual(void) { struct sigaction tact; tact.sa_handler = timeout_info_timer_virtual; tact.sa_flags = 0; sigemptyset (&tact.sa_mask); //sigemptyset is used to initialize and clear the parameter set signal set. sigaction(SIGVTALRM, &tact, NULL);//Establish signal processing mechanism} /* Timer operation*/ /* Function name: timeout_info Function: Timing operation content input: not used*/ void timeout_info_timer_virtual(int signo)//Timing operation Content { printf("timer = %d\n",bbb++); } ``` After writing the code and saving it, compile it. At 18:10, the compiler started compiling and the following error occurred: [attach]562206 [/attach] It was not until 20:14 that I went out for lunch and came back. After compiling again (without making any changes to the program), the program passed without any errors. :Onion-18: What went wrong? Is it a compiler problem?</stdio.h></errno.h></unistd.h></signal.h></sys></time.h></sched.h></unistd.h>

Jacktang

It's not a compiler problem, after all, the compilation was successful in the end

Or it may be related to the dynamic library used

bqgup

Jacktang posted on 2021-9-10 13:24 It is not a compiler problem. After all, the compilation was successful in the end. Or it is related to the dynamic library used

At the beginning of the compilation, it always reported an error saying that the variable was not defined, and the compiler was stupid.