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authorAndy Lutomirski <luto@amacapital.net>2014-12-03 15:37:08 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-03 20:55:58 -0800
commit7cc78f8fa02c2485104b86434acbc1538a3bd807 (patch)
treef3a9fdccb6f2c4db996299fe23f6597592b30085
parentebcd241a635c868b1f89abbfb4dd176ca5f81eba (diff)
downloadlinux-linaro-stable-7cc78f8fa02c2485104b86434acbc1538a3bd807.tar.gz
context_tracking: Restore previous state in schedule_user
It appears that some SCHEDULE_USER (asm for schedule_user) callers in arch/x86/kernel/entry_64.S are called from RCU kernel context, and schedule_user will return in RCU user context. This causes RCU warnings and possible failures. This is intended to be a minimal fix suitable for 3.18. Reported-and-tested-by: Dave Jones <davej@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Frédéric Weisbecker <fweisbec@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/sched/core.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 24beb9b..89e7283 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2874,10 +2874,14 @@ asmlinkage __visible void __sched schedule_user(void)
* or we have been woken up remotely but the IPI has not yet arrived,
* we haven't yet exited the RCU idle mode. Do it here manually until
* we find a better solution.
+ *
+ * NB: There are buggy callers of this function. Ideally we
+ * should warn if prev_state != IN_USER, but that will trigger
+ * too frequently to make sense yet.
*/
- user_exit();
+ enum ctx_state prev_state = exception_enter();
schedule();
- user_enter();
+ exception_exit(prev_state);
}
#endif