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| author | Andy Lutomirski <luto@amacapital.net> | 2014-12-04 02:37:08 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-04 07:55:58 +0300 |
| commit | 7cc78f8fa02c2485104b86434acbc1538a3bd807 (patch) | |
| tree | f3a9fdccb6f2c4db996299fe23f6597592b30085 | |
| parent | ebcd241a635c868b1f89abbfb4dd176ca5f81eba (diff) | |
| download | linux-7cc78f8fa02c2485104b86434acbc1538a3bd807.tar.xz | |
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.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 24beb9bb4c3e..89e7283015a6 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 |