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* inferior.h (enum stop_kind): Improve comment.

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Doug Evans 2014-03-30 12:24:31 -07:00
parent 97d8f0ee77
commit 7c0bc051fc
2 changed files with 12 additions and 8 deletions
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gdb/ChangeLog
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@ -1,3 +1,7 @@
2014-03-30 Doug Evans <xdje42@gmail.com>
* inferior.h (enum stop_kind): Improve comment.
2014-03-28 Joel Brobecker <brobecker@adacore.com>
* varobj.c (varobj_value_has_mutated): If NEW_VALUE is

16
gdb/inferior.h
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@ -305,20 +305,20 @@ enum step_over_calls_kind
setting up a remote connection; it is like STOP_QUIETLY_NO_SIGSTOP
except that there is no need to hide a signal. */
/* It is also used after attach, due to attaching to a process. This
is a bit trickier. When doing an attach, the kernel stops the
debuggee with a SIGSTOP. On newer GNU/Linux kernels (>= 2.5.61)
the handling of SIGSTOP for a ptraced process has changed. Earlier
versions of the kernel would ignore these SIGSTOPs, while now
SIGSTOP is treated like any other signal, i.e. it is not muffled.
/* STOP_QUIETLY_NO_SIGSTOP is used to handle a tricky situation with attach.
When doing an attach, the kernel stops the debuggee with a SIGSTOP.
On newer GNU/Linux kernels (>= 2.5.61) the handling of SIGSTOP for
a ptraced process has changed. Earlier versions of the kernel
would ignore these SIGSTOPs, while now SIGSTOP is treated like any
other signal, i.e. it is not muffled.
If the gdb user does a 'continue' after the 'attach', gdb passes
the global variable stop_signal (which stores the signal from the
attach, SIGSTOP) to the ptrace(PTRACE_CONT,...) call. This is
problematic, because the kernel doesn't ignore such SIGSTOP
now. I.e. it is reported back to gdb, which in turn presents it
back to the user.
To avoid the problem, we use STOP_QUIETLY_NO_SIGSTOP, which allows
gdb to clear the value of stop_signal after the attach, so that it
is not passed back down to the kernel. */