Mastering Linux Kernel Development

Signal delivery

After a signal is generated by updating appropriate entries in the receiver's task structure, through any of the previously mentioned signal-generation calls, the kernel moves into delivery mode. The signal is instantly delivered if the receiver process was on CPU and has not blocked the specified signal. Priority signals SIGSTOP and SIGKILL are delivered even if the receiver is not on CPU by waking up the process; however, for the rest of the signals, delivery is deferred until the process is ready to receive signals. To facilitate deferred delivery, the kernel checks for nonblocked pending signals of a process on return from interrupt and system calls before allowing a process to resume user-mode execution. When the process ...