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don't stop in issignal() if P_SINGLE_EXIT is set

Description

don't stop in issignal() if P_SINGLE_EXIT is set

Suppose a traced process is stopped in ptracestop() due to receipt of a
SIGSTOP signal, and is awaiting orders from the tracing process on how
to handle the signal. Before sending any such orders, the tracing
process exits. This should kill the traced process. But suppose a second
thread handles the SIGKILL and proceeds to exit1(), calling
thread_single(). The first thread will now awaken and will have a chance
to check once more if it should go to sleep due to the SIGSTOP. It must
not sleep after P_SINGLE_EXIT has been set; this would prevent the
SIGKILL from taking effect, leaving a stopped orphan behind after the
tracing process dies.

Also add new tests for this condition.

Reviewed by: kib
MFC after: 2 weeks
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D9890

Details

Committed
badgerMar 7 2017, 1:41 PM
Reviewer
kib
Differential Revision
D9890: don't stop in issignal() if P_SINGLE_EXIT is set
Parents
rS314851: When selecting brand based on old Elf branding, prefer the brand which
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