Date: Tue, 26 Aug 2014 15:09:26 -0400 From: John Baldwin <jhb@freebsd.org> To: "John-Mark Gurney" <jmg@funkthat.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Mateusz Guzik <mjguzik@gmail.com>, src-committers@freebsd.org, Mateusz Guzik <mjg@freebsd.org> Subject: Re: svn commit: r270444 - in head/sys: kern sys Message-ID: <201408261509.26815.jhb@freebsd.org> In-Reply-To: <20140825223034.GE71691@funkthat.com> References: <201408240904.s7O949sI083660@svn.freebsd.org> <1815651.yxLDiBYvJT@ralph.baldwin.cx> <20140825223034.GE71691@funkthat.com>
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On Monday, August 25, 2014 6:30:34 pm John-Mark Gurney wrote: > John Baldwin wrote this message on Mon, Aug 25, 2014 at 13:35 -0400: > > On Monday, August 25, 2014 07:02:41 PM Mateusz Guzik wrote: > > > On Mon, Aug 25, 2014 at 10:23:19AM -0400, John Baldwin wrote: > > > > On Sunday, August 24, 2014 09:04:09 AM Mateusz Guzik wrote: > > > > > Author: mjg > > > > > Date: Sun Aug 24 09:04:09 2014 > > > > > New Revision: 270444 > > > > > URL: http://svnweb.freebsd.org/changeset/base/270444 > > > > > > > > > > Log: > > > > > Fix getppid for traced processes. > > > > > > > > > > Traced processes always have the tracer set as the parent. > > > > > Utilize proc_realparent to obtain the right process when needed. > > > > > > > > Are you sure this won't break things? I know of several applications that > > > > expect a debugger to be the parent when attached and change behavior as a > > > > result (e.g. inserting a breakpoint on an assertion failure rather than > > > > generating a core). > > > > > > Well, this is what linux and solaris do. > > > > Interesting. > > > > > I don't feel strongly about this change. If you really want I'm happy to > > > revert. > > > > In general I'd like to someday have the debugger-debuggee relationship not > > override parent-child and this is a step in that direction. However, this > > will break existing applications, so this needs to be clearly documented in > > the release notes. In addition, we should probably advertise how a process > > can correctly determine if it is being run under a debugger (right now you can > > do 'getppid()' and use strcmp or strstr on the p_comm of that pid so you can > > do different things for "gdb" vs "gcore", etc. so just checking P_TRACED from > > kinfo_proc wouldn't be equivalent in functionality) > > But what about when you attach gdb to a running process... That > doesn't magicly make the now debugged process a child of gdb does it? % cat hello.c #include <stdio.h> int main() { printf("hello world\n"); (void)getchar(); return (0); } % cc -g hello.c -o hello % ./hello hello world load: 9.81 cmd: hello 42599 [ttyin] 1.67r 0.00u 0.00s 0% 1056k < different window > % ps -O ppid -p `pgrep hello` PID PPID TT STAT TIME COMMAND 42599 5340 16 I+ 0:00.00 ./hello % gdb hello `pgrep hello` GNU gdb 6.1.1 [FreeBSD] ... (gdb) <hit Ctrl-Z> Suspended % ps -O ppid -p `pgrep hello` PID PPID TT STAT TIME COMMAND 42599 45079 16 TX+ 0:00.00 ./hello -- John Baldwin
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