context_tracking: Restore previous state in schedule_user (7cc78f8f) · Commits · 戴 / test

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>

kernel/sched/core.c

+6 −2

Original line number	Original line	Diff line number	Diff line
	@@ -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,		* 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 haven't yet exited the RCU idle mode. Do it here manually until
	* we find a better solution.		* 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();		schedule();
	user_enter();		exception_exit(prev_state);
	}		}
	#endif		#endif

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