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s390/idle: fix suspicious RCU usage

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After commit eb1f00237aca ("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>
This commit is contained in:
Peter Zijlstra 2020-09-08 15:30:31 +02:00 committed by Vasily Gorbik
parent 856deb866d
commit ca589ea8d1
1 changed files with 2 additions and 3 deletions
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5
arch/s390/kernel/idle.c
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@ -39,14 +39,13 @@ void enabled_wait(void)
local_irq_restore(flags); local_irq_restore(flags);
/* Account time spent with enabled wait psw loaded as idle time. */ /* Account time spent with enabled wait psw loaded as idle time. */
/* XXX seqcount has tracepoints that require RCU */ raw_write_seqcount_begin(&idle->seqcount);
write_seqcount_begin(&idle->seqcount);
idle_time = idle->clock_idle_exit - idle->clock_idle_enter; idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
idle->clock_idle_enter = idle->clock_idle_exit = 0ULL; idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
idle->idle_time += idle_time; idle->idle_time += idle_time;
idle->idle_count++; idle->idle_count++;
account_idle_time(cputime_to_nsecs(idle_time)); account_idle_time(cputime_to_nsecs(idle_time));
write_seqcount_end(&idle->seqcount); raw_write_seqcount_end(&idle->seqcount);
} }
NOKPROBE_SYMBOL(enabled_wait); NOKPROBE_SYMBOL(enabled_wait);