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Special-case wildcard requests in ravenscar-thread.c 

ravenscar-thread.c intercepts resume and wait target requests and
replaces the requested ptid with the ptid of the underlying CPU.
However, this is incorrect when a request is made with a wildcard
ptid.

This patch adds a special case to ravenscar-thread.c for
minus_one_ptid.  I don't believe a special case for process wildcards
is necessary, so I have not added that.

Joel's description explains the bug well:

At the user level, we noticed the issue because we had a test were
we insert a breakpoint one some code which is only run from, say,
CPU #2, whereas we unfortunately resumed the execution after having
stopped somewhere in CPU #1. As a result, we sent an order to resume
CPU #1, which starves CPU #2 forever, because the code in CPU #1
waits for some of the Ada tasks allocated to CPU #2 (and we never
reach our breakpoint either).

gdb/ChangeLog
2019-02-15  Tom Tromey  <tromey@adacore.com>

	* ravenscar-thread.c (ravenscar_thread_target::resume)
	(ravenscar_thread_target::wait): Special case wildcard requests.
This commit is contained in:
Tom Tromey 2019-02-06 15:14:40 +01:00
parent 0b790b1eeb
commit 485b851b68
2 changed files with 15 additions and 2 deletions
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5
gdb/ChangeLog
View File

@ -1,3 +1,8 @@
2019-02-15 Tom Tromey <tromey@adacore.com>
* ravenscar-thread.c (ravenscar_thread_target::resume)
(ravenscar_thread_target::wait): Special case wildcard requests.
2019-02-15 Tom Tromey <tromey@adacore.com>
* ravenscar-thread.c (base_ptid): Remove.

12
gdb/ravenscar-thread.c
View File

@ -323,8 +323,12 @@ void
ravenscar_thread_target::resume (ptid_t ptid, int step,
enum gdb_signal siggnal)
{
/* If we see a wildcard resume, we simply pass that on. Otherwise,
arrange to resume the base ptid. */
inferior_ptid = m_base_ptid;
beneath ()->resume (m_base_ptid, step, siggnal);
if (ptid != minus_one_ptid)
ptid = m_base_ptid;
beneath ()->resume (ptid, step, siggnal);
}
ptid_t
@ -335,7 +339,9 @@ ravenscar_thread_target::wait (ptid_t ptid,
ptid_t event_ptid;
inferior_ptid = m_base_ptid;
event_ptid = beneath ()->wait (m_base_ptid, status, 0);
if (ptid != minus_one_ptid)
ptid = m_base_ptid;
event_ptid = beneath ()->wait (ptid, status, 0);
/* Find any new threads that might have been created, and update
inferior_ptid to the active thread.
@ -350,6 +356,8 @@ ravenscar_thread_target::wait (ptid_t ptid,
this->update_thread_list ();
this->update_inferior_ptid ();
}
else
inferior_ptid = m_base_ptid;
return inferior_ptid;
}