Commit ca589ea8 authored Sep 08, 2020 by Peter Zijlstra Committed by Vasily Gorbik Sep 14, 2020

s390/idle: fix suspicious RCU usage



After commit eb1f0023 ("lockdep,trace: Expose tracepoints") the
lock tracepoints are visible to lockdep and RCU-lockdep is finding a
bunch more RCU violations that were previously hidden.

Switch the idle->seqcount over to using raw_write_*() to avoid the
lockdep annotation and thus the lock tracepoints.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

parent 856deb86

arch/s390/kernel/idle.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -39,14 +39,13 @@ void enabled_wait(void)
		local_irq_restore(flags);

		/* Account time spent with enabled wait psw loaded as idle time. */
		/* XXX seqcount has tracepoints that require RCU */
		write_seqcount_begin(&idle->seqcount);
		raw_write_seqcount_begin(&idle->seqcount);
		idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
		idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
		idle->idle_time += idle_time;
		idle->idle_count++;
		account_idle_time(cputime_to_nsecs(idle_time));
		write_seqcount_end(&idle->seqcount);
		raw_write_seqcount_end(&idle->seqcount);
		}
		NOKPROBE_SYMBOL(enabled_wait);

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