Question

I have a program in Linux which is multithreaded. There are certain memory areas in which I’m interested to see if they have been written within a certain time period. For that I give only read access to those memory pages and install a signal handler for SIGSEGV. Now my question is, will each thread call the signal handler for itself. Say Thread 1 writes to some forbidden memory area, will it be the one to execute the signal handler?

Answer 1

First of all

Signal dispositions are process-wide;
all threads in a process share the
same disposition for each signal. If
one thread uses sigaction() to
establish a handler for, say, SIGINT,
then that handler may be invoked from
any thread to which the SIGINT is
delivered.

But read on

A signal may be directed to either the
process as a whole or to a specific
thread. A signal is thread-directed if

it is generated as the direct result
of the execution of a specific
hardware instruction within the
context of the thread (SIGBUS, SIGFPE, SIGILL, and SIGSEGV)

I am quoting from TLPI.