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| author | Peter Zijlstra <peterz@infradead.org> | 2015-02-09 11:53:18 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-18 14:11:12 +0100 |
| commit | 5746f2d2f1fad069e2de754310b62e19440c0080 (patch) | |
| tree | 06c0db09f5a920c5e4fcbcaad0b84b8be5b85a72 | |
| parent | abe2114079571ffcbb410a3b427e528674526a1b (diff) | |
| download | lwn-5746f2d2f1fad069e2de754310b62e19440c0080.tar.gz lwn-5746f2d2f1fad069e2de754310b62e19440c0080.zip | |
sched/autogroup: Fix failure to set cpu.rt_runtime_us
commit 1fe89e1b6d270aa0d3452c60d38461ea589594e3 upstream.
Because task_group() uses a cache of autogroup_task_group(), whose
output depends on sched_class, switching classes can generate
problems.
In particular, when started as fair, the cache points to the
autogroup, so when switching to RT the tg_rt_schedulable() test fails
for every cpu.rt_{runtime,period}_us change because now the autogroup
has tasks and no runtime.
Furthermore, going back to the previous semantics of varying
task_group() with sched_class has the down-side that the sched_debug
output varies as well, even though the task really is in the
autogroup.
Therefore add an autogroup exception to tg_has_rt_tasks() -- such that
both (all) task_group() usages in sched/core now have one. And remove
all the remnants of the variable task_group() output.
Reported-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Stefan Bader <stefan.bader@canonical.com>
Fixes: 8323f26ce342 ("sched: Fix race in task_group()")
Link: http://lkml.kernel.org/r/20150209112237.GR5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/sched/auto_group.c | 6 | ||||
| -rw-r--r-- | kernel/sched/core.c | 6 |
2 files changed, 7 insertions, 5 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index 8a2e230fb86a..eae160dd669d 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -87,8 +87,7 @@ static inline struct autogroup *autogroup_create(void) * so we don't have to move tasks around upon policy change, * or flail around trying to allocate bandwidth on the fly. * A bandwidth exception in __sched_setscheduler() allows - * the policy change to proceed. Thereafter, task_group() - * returns &root_task_group, so zero bandwidth is required. + * the policy change to proceed. */ free_rt_sched_group(tg); tg->rt_se = root_task_group.rt_se; @@ -115,9 +114,6 @@ bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) if (tg != &root_task_group) return false; - if (p->sched_class != &fair_sched_class) - return false; - /* * We can only assume the task group can't go away on us if * autogroup_move_group() can see us on ->thread_group list. diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 48c50118b17a..44dfc8b46bd0 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7618,6 +7618,12 @@ static inline int tg_has_rt_tasks(struct task_group *tg) { struct task_struct *g, *p; + /* + * Autogroups do not have RT tasks; see autogroup_create(). + */ + if (task_group_is_autogroup(tg)) + return 0; + for_each_process_thread(g, p) { if (rt_task(p) && task_group(p) == tg) return 1; |