PR/51420 CVS commit: [netbsd-9] src

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

The following reply was made to PR kern/51420; it has been noted by GNATS.

From: "Martin Husemann" <martin%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/51420 CVS commit: [netbsd-9] src
Date: Wed, 23 Oct 2019 19:25:39 +0000

 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.