CVS commit: [netbsd-9] src

["Martin Husemann" <martin%netbsd.org@localhost>]

Module Name:    src
Committed By:   martin
Date:           Wed Oct 23 19:25:39 UTC 2019

Modified Files:
        src/sys/kern [netbsd-9]: kern_sig.c sys_ptrace_common.c
        src/tests/lib/libc/sys [netbsd-9]: t_ptrace_wait.c

Log Message:
Pull up following revision(s) (requested by kamil in ticket #366):

        tests/lib/libc/sys/t_ptrace_wait.c: revision 1.136
        sys/kern/kern_sig.c: revision 1.373
        tests/lib/libc/sys/t_ptrace_wait.c: revision 1.138
        tests/lib/libc/sys/t_ptrace_wait.c: revision 1.139
        sys/kern/kern_sig.c: revision 1.376
        tests/lib/libc/sys/t_ptrace_wait.c: revision 1.140
        sys/kern/sys_ptrace_common.c: revision 1.64

Fix typo in a comment

Enable TEST_LWP_ENABLED in t_ptrace_wait*
The LWP events (created, exited) are now reliable in my local tests.
PR kern/51420
PR kern/51995

Remove the short-circuit lwp_exit() path from sigswitch()

sigswitch() can be called from exit1() through:

   ttywait()->ttysleep()-> cv_timedwait_sig()->sleepq_block()->issignal()->sigswitch()

lwp_exit() called for the last LWP triggers exit1() and this causes a panic.
The debugger related signals have short-circuit demise paths in
eventswitch() and other functions, before calling sigswitch().

This change restores the original behavior, but there is an open question
whether the kernel crash is a red herring of misbehavior of ttywait().
This should fix PR kern/54618 by David H. Gutteridge

Fix a race condition when handling concurrent LWP signals and add a test

Fix a race condition that caused PT_GET_SIGINFO to return incorrect
information when multiple signals were delivered concurrently
to different LWPs.  Add a regression test that verifies that when 50
threads concurrently use pthread_kill() on themselves, the debugger
receives all signals with correct information.

The kernel uses separate signal queues for each LWP.  However,
the signal context used to implement PT_GET_SIGINFO is stored in 'struct
proc' and therefore common to all LWPs in the process.  Previously,
this member was filled in kpsignal2(), i.e. when the signal was sent.

This meant that if another LWP managed to send another signal
concurrently, the data was overwritten before the process was stopped.

As a result, PT_GET_SIGINFO did not report the correct LWP and signal
(it could even report a different signal than wait()).  This can be
quite reliably reproduced with the number of 20 LWPs, however it can
also occur with 10.

This patch moves setting of signal context to issignal(), just before
the process is actually stopped.  The data is taken from per-LWP
or per-process signal queue.  The added test confirms that the debugger
correctly receives all signals, and PT_GET_SIGINFO reports both correct
LWP and signal number.
Reviewed by kamil.

Remove preprocessor switch TEST_VFORK_ENABLED in t_ptrace_wait*
vfork(2) tests are now enabled always and confirmed to be stable.

Remove preprocessor switch TEST_LWP_ENABLED in t_ptrace_wait*
LWP tests are now enabled always and confirmed to be stable.


To generate a diff of this commit:
cvs rdiff -u -r1.364.2.7 -r1.364.2.8 src/sys/kern/kern_sig.c
cvs rdiff -u -r1.58.2.8 -r1.58.2.9 src/sys/kern/sys_ptrace_common.c
cvs rdiff -u -r1.131.2.5 -r1.131.2.6 src/tests/lib/libc/sys/t_ptrace_wait.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.