Re: ttrace: Protocal error

[John David Anglin <dave@hiauly1.hia.nrc.ca>]

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On Sat, 09 Aug 2008, Pedro Alves wrote:

> If I'm analising the race correctly, an alternative simpler solution
> to the above, would be to just ignore a failed resume on a
> dying thread, but still try to resume it.  Not resuming dying threads
> may be a problem.

It occured to me that my suggested change wasn't going to handle the
race associated with threads dying, although it improves the situation.

The ttrace documentation suggested that only stopped threads should
be resumed.  The thread info indicated the thread in question was
running.  I changed the code to only check for thread stopped.  However,
this didn't work.  My testcase hangs when run under gdb:

(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y

Starting program: /mnt/gnu/gcc/objdir/hppa2.0w-hp-hpux11.11/libgomp/testsuite/vla6.x3g 
warning: Private mapping of shared library text was not specified
by the executable; setting a breakpoint in a shared library which
is not privately mapped will not work.  See the HP-UX 11i v3 chatr
manpage for methods to privately map shared library text.
[New process 2316, lwp 7552188]
[process 2316, lwp 7552188 exited]
[New process 2316, lwp 7552189]
[process 2316, lwp 7552189 exited]
[New process 2316, lwp 7552190]
[process 2316, lwp 7552190 exited]
[New process 2316, lwp 7552191]
[process 2316, lwp 7552191 exited]
[New process 2316, lwp 7552192]
[New process 2316, lwp 7552193]
[New process 2316, lwp 7552194]
[New process 2316, lwp 7552195]
[New process 2316, lwp 7552196]

Program received signal SIGINT, Interrupt.
[Switching to process 2316, lwp 7552196]
0xc03bea58 in __lwp_sema_wait () from /usr/lib/librt.2

So, there's apparently a race in detection when a program is stopped.
It looks like we need to try your suggestion(s).

Attached same with debug infrun 1.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)

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(gdb) set debug infrun 1
(gdb) r
Starting program: /mnt/gnu/gcc/objdir/hppa2.0w-hp-hpux11.11/libgomp/testsuite/vla6.x3g 
infrun: wait_for_inferior (treat_exec_as_sigtrap=1)
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x91d0
infrun: quietly stopped
infrun: stop_stepping
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: wait_for_inferior (treat_exec_as_sigtrap=1)
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x19f8
infrun: quietly stopped
infrun: stop_stepping
warning: Private mapping of shared library text was not specified
by the executable; setting a breakpoint in a shared library which
is not privately mapped will not work.  See the HP-UX 11i v3 chatr
manpage for methods to privately map shared library text.
infrun: proceed (addr=0xffffffff, signal=0, step=0)
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: wait_for_inferior (treat_exec_as_sigtrap=0)
[New process 2557, lwp 7552464]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[process 2557, lwp 7552464 exited]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552465]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[process 2557, lwp 7552465 exited]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552466]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[process 2557, lwp 7552466 exited]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552467]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[process 2557, lwp 7552467 exited]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x19e0
infrun: BPSTAT_WHAT_CHECK_SHLIBS
infrun: no stepping, continue
infrun: resume (step=1, signal=0), stepping_over_breakpoint=1
infrun: prepare_to_wait
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x19e4
infrun: no stepping, continue
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552468]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552469]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552470]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552471]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
[New process 2557, lwp 7552472]
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_SPURIOUS
infrun: resume (step=0, signal=0), stepping_over_breakpoint=0
infrun: prepare_to_wait
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0xc020c878
infrun: context switch
infrun: Switching context from process 2557, lwp 7552460 to process 2557, lwp 7552472
infrun: random signal 2

Program received signal SIGINT, Interrupt.
infrun: stop_stepping
[Switching to process 2557, lwp 7552472]
0xc020c878 in __ksleep () from /usr/lib/libc.2