From b0319eaaf9d1f4e730c532058f2fff0b4e5ce682 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Thu, 4 Apr 2019 16:57:11 -0600 Subject: [PATCH] Use find_thread_in_random in select_event_lwp I noticed that find_thread_in_random duplicates the code in find_thread_in_random, so this patch changes the latter to use the former. There are two other spots in gdb that do this, but to unify all of them would require switching some code from using the "iterate over" idiom to using iterators. Another possible improvement is that find_thread_in_random could be made single-pass using reservoir sampling. Tested by the buildbot. gdb/gdbserver/ChangeLog 2019-04-09 Tom Tromey * linux-low.c (select_event_lwp): Use find_thread_in_random. --- gdb/gdbserver/ChangeLog | 4 ++++ gdb/gdbserver/linux-low.c | 35 ++++------------------------------- 2 files changed, 8 insertions(+), 31 deletions(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index e82e901564..1618e2c4b0 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,7 @@ +2019-04-09 Tom Tromey + + * linux-low.c (select_event_lwp): Use find_thread_in_random. + 2019-04-08 Tom Tromey * linux-low.c (linux_detach_one_lwp): Replace throw_exception with diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index 94af240a5c..168f4b2abc 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -2828,7 +2828,6 @@ linux_wait_for_event (ptid_t ptid, int *wstatp, int options) static void select_event_lwp (struct lwp_info **orig_lp) { - int random_selector; struct thread_info *event_thread = NULL; /* In all-stop, give preference to the LWP that is being @@ -2862,39 +2861,13 @@ select_event_lwp (struct lwp_info **orig_lp) /* No single-stepping LWP. Select one at random, out of those which have had events. */ - /* First see how many events we have. */ - int num_events = 0; - for_each_thread ([&] (thread_info *thread) - { - lwp_info *lp = get_thread_lwp (thread); - - /* Count only resumed LWPs that have an event pending. */ - if (thread->last_status.kind == TARGET_WAITKIND_IGNORE - && lp->status_pending_p) - num_events++; - }); - gdb_assert (num_events > 0); - - /* Now randomly pick a LWP out of those that have had - events. */ - random_selector = (int) - ((num_events * (double) rand ()) / (RAND_MAX + 1.0)); - - if (debug_threads && num_events > 1) - debug_printf ("SEL: Found %d SIGTRAP events, selecting #%d\n", - num_events, random_selector); - - event_thread = find_thread ([&] (thread_info *thread) + event_thread = find_thread_in_random ([&] (thread_info *thread) { lwp_info *lp = get_thread_lwp (thread); - /* Select only resumed LWPs that have an event pending. */ - if (thread->last_status.kind == TARGET_WAITKIND_IGNORE - && lp->status_pending_p) - if (random_selector-- == 0) - return true; - - return false; + /* Only resumed LWPs that have an event pending. */ + return (thread->last_status.kind == TARGET_WAITKIND_IGNORE + && lp->status_pending_p); }); } -- 2.34.1