Fix multiprocessing regression on newer glibcs

Merged Bitbucket Importer requested to merge bitbucket/merged-pr-607 into branch/py3.5

Created originally on Bitbucket by hroncok (Miro Hrončok)

Was already merged in Bitbucket before import, marked as merged by the import user

Fix multiprocessing regression on newer glibcs

Starting with glibc 2.27.9000-xxx, sigaddset() can return EINVAL for some reserved signal numbers between 1 and NSIG. The range(1, NSIG) idiom is commonly used to select all signals for blocking with pthread_sigmask. So we ignore the sigaddset() return value until we expose sigfillset() to provide a better idiom.

Co-authored-by: Antoine Pitrou

Merge request reports