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rt_sigprocmask - examine and change a signal mask


rt_sigprocmask is a system call used to examine and change a signal mask for a process. The signal mask is a set of signals used to control what signals are blocked and thus not delivered to a process. It also allows for the manipulation of the process' signal mask atomically (in one instruction). The rt_sigprocmask system call is a realtime version of the sigprocmask system call, and will preserve the realtime signals.

There are some edge cases to be aware of when using rt_sigprocmask. For example, if the sigsetsize parameter is greater than the size of a sigset_t (128 bytes on 64-bit architectures), then the call will fail with EINVAL.


  • how:int - Specifies how the signal mask is to be changed. It is one of the following constants:
  • SIG_BLOCK: The resulting set is the union of the current set and the set argument.
  • SIG_UNBLOCK: The resulting set is the intersection of the current set and the complement of the set argument.
  • SIG_SETMASK: The resulting set is the set argument.
  • set:sigset_t*[K] - Pointer to a signal set whose elements will be added (SIG_BLOCK) or deleted (SIG_UNBLOCK) from the current set.
  • oldset:sigset_t* - Pointer to a signal set which will be filled with the old signal mask.
  • sigsetsize:size_t - The size of the signal set oldset in bytes.

Available Tags

  • K - Originated from kernel-space.






This function is hooked to enable monitoring of the behavior of the rt_sigprocmask system call. With this hook, you can monitor when the system call is called and how long the call takes.

Example Use Case

One example of where this event could be useful is in monitoring system calls for benchmarking applications. By monitoring the rt_sigprocmask system call you can measure how long this system call takes to execute, which can give an indication of how fast the overall application is.


One issue to be aware of when using this system call is that it is vulnerable to a time-of-check-to-time-of-use (TOCTOU) race condition due to the fact that the signal mask can be changed between the time of the check and the time of the use.

  • rt_sigaction()
  • sigprocmask()

This document was automatically generated by OpenAI and needs review. It might not be accurate and might contain errors. The authors of Tracee recommend that the user reads the "events.go" source file to understand the events and their arguments better.