Commit-ID: 1dc0fffc48af94513e621f95dff730ed4f7317ec
Gitweb: http://git.kernel.org/tip/1dc0fffc48af94513e621f95dff730ed4f7317ec
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 28 Sep 2015 17:57:39 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 6 Oct 2015 17:08:17 +0200
sched/core: Robustify preemption leak checks
When we warn about a preempt_count leak; reset the preempt_count to
the known good value such that the problem does not ripple forward.
This is most important on x86 which has a per cpu preempt_count that is
not saved/restored (after this series). So if you schedule with an
invalid (!2*PREEMPT_DISABLE_OFFSET) preempt_count the next task is
messed up too.
Enforcing this invariant limits the borkage to just the one task.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/exit.c | 4 +++-
kernel/sched/core.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index ea95ee1..443677c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -706,10 +706,12 @@ void do_exit(long code)
smp_mb();
raw_spin_unlock_wait(&tsk->pi_lock);
- if (unlikely(in_atomic()))
+ if (unlikely(in_atomic())) {
pr_info("note: %s[%d] exited with preempt_count %d\n",
current->comm, task_pid_nr(current),
preempt_count());
+ preempt_count_set(PREEMPT_ENABLED);
+ }
/* sync mm's RSS info before statistics gathering */
if (tsk->mm)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6344d82..d6989f8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2968,8 +2968,10 @@ static inline void schedule_debug(struct task_struct *prev)
BUG_ON(unlikely(task_stack_end_corrupted(prev)));
#endif
- if (unlikely(in_atomic_preempt_off()))
+ if (unlikely(in_atomic_preempt_off())) {
__schedule_bug(prev);
+ preempt_count_set(PREEMPT_DISABLED);
+ }
rcu_sleep_check();
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
--
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