From 9516f85aea1d9a34d1cd3f59b7b9eeb590e58c70 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Wed, 23 May 2018 14:25:20 +0100 Subject: [PATCH] gdb: Mark async event handler when event is already pending In PR22882 inferior functions are called on different threads while scheduler-locking is turned on. This results in a hang. This was discussed in this mailing list thread: https://sourceware.org/ml/gdb/2017-10/msg00032.html The problem is that when the thread is set running in order to execute the inferior call, a call to target_async is made. If the target is not already registered as 'target_async' then this will install the async event handler, AND unconditionally mark the handler as having an event pending. However, if the target is already registered as target_async then the event handler is not installed (its already installed) and the handler is NOT marked as having an event pending. If we try to set running a thread that already has a pending event, then we do want to set target_async, however, there will not be an external event incoming (the thread is already stopped) so we rely on manually marking the event handler as having a pending event in order to see the threads pending stop event. This is fine, if, at the point where we call target_async, the target is not already marked as async. But, if it is, then the event handler will not be marked as ready, and the threads pending stop event will never be processed. A similar pattern of code can be seen in linux_nat_target::resume, where, when a thread has a pending event, the call to target_async is followed by a call to async_file_mark to ensure that the pending thread event will be processed, even if target_async was already set. gdb/ChangeLog: PR gdb/22882 * infrun.c (resume_1): Add call to mark_async_event_handler. gdb/testsuite/ChangeLog: * gdb.threads/multiple-successive-infcall.exp: Remove kfail case, rewrite test to describe action performed, rather than possible failure. --- gdb/ChangeLog | 6 ++++++ gdb/infrun.c | 6 +++++- gdb/testsuite/ChangeLog | 7 +++++++ gdb/testsuite/gdb.threads/multiple-successive-infcall.exp | 15 ++------------- 4 files changed, 20 insertions(+), 14 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index e05561a..692bb5a 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,4 +1,10 @@ 2018-06-12 Andrew Burgess + Stephen Roberts + + PR gdb/22882 + * infrun.c (resume_1): Add call to mark_async_event_handler. + +2018-06-12 Andrew Burgess * infrun.c (do_target_wait): Change old version of $pc printed. diff --git a/gdb/infrun.c b/gdb/infrun.c index 655681f..6f5338c 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -2408,7 +2408,11 @@ resume_1 (enum gdb_signal sig) tp->suspend.stop_signal = GDB_SIGNAL_0; if (target_can_async_p ()) - target_async (1); + { + target_async (1); + /* Tell the event loop we have an event to process. */ + mark_async_event_handler (infrun_async_inferior_event_token); + } return; } diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 2324673..0059828 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,10 @@ +2018-06-12 Andrew Burgess + Stephen Roberts + + * gdb.threads/multiple-successive-infcall.exp: Remove kfail case, + rewrite test to describe action performed, rather than possible + failure. + 2018-06-08 Gary Benson * gdb.threads/check-libthread-db.exp: New file. diff --git a/gdb/testsuite/gdb.threads/multiple-successive-infcall.exp b/gdb/testsuite/gdb.threads/multiple-successive-infcall.exp index a71f991..bb92c1d 100644 --- a/gdb/testsuite/gdb.threads/multiple-successive-infcall.exp +++ b/gdb/testsuite/gdb.threads/multiple-successive-infcall.exp @@ -56,17 +56,6 @@ gdb_test "show scheduler-locking" \ foreach_with_prefix thread {5 4 3 2 1} { gdb_test "thread ${thread}" "Switching to .*" - set command "call get_value()" - set hang_message "testing if ${command} hangs" - gdb_test_multiple "${command}" "${hang_message}" { - -re "= ${thread}\[\r\n]+${gdb_prompt} $" { - pass "${hang_message}" - } - timeout { - kfail "gdb/22882" "${hang_message}" - # Exit. The debugger has hung, so there is no point in wasting - # time timing out on further calls to get_value(). - return 0 - } - } + gdb_test "call get_value()" "= ${thread}" \ + "call inferior function" } -- 2.7.4