Re: Can fork be used in a signal handler?

kiran <edu.mvk@xxxxxxxxx> writes:
I have a problem that i have to create a new process, when my process
gets a SIGCHLD.
So i want to use fork inside the signal handler for SIGCHLD.

Have you read the documentation for the operating system you're using?
You didn't say what you're using, but on Solaris I see this for
fork(2):

| MT-Level | Async-Signal-Safe. |

and the attributes(5) page says:

Async-Signal-Safe

Async-Signal-Safe refers to particular library functions
that can be safely called from a signal handler. A
thread that is executing an Async-Signal-Safe function
will not deadlock with itself if interrupted by a sig-
nal. Signals are only a problem for MT-Safe functions
that acquire locks.

Async-Signal-Safe functions are also MT-Safe. Signals
are disabled when locks are acquired in Async-Signal-
Safe functions. These signals prevent a signal handler
that might acquire the same lock from being called.

So, you can do it there at least.

And in the signal handler i'm traversing a linked list which has the
complexity of O(n2). Is that ok if a signal handler to be that heavy?
Note: no global variables are being changed inside the handler.

That's something you'll have to evaluate on your own. Nobody here
knows the underlying requirements or detailed design of your program.

--
James Carlson, Solaris Networking <james.d.carlson@xxxxxxx>
Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
.

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