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srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap 

SRCU checks each srcu_data structure's grace-period number for counter
wrap four times per cycle by default.  This frequency guarantees that
normal comparisons will detect potential wrap.  However, the expedited
grace-period number is not checked.  The consquences are not too horrible
(a failure to expedite a grace period when requested), but it would be
good to avoid such things.  This commit therefore adds this check to
the expedited grace-period number.

Signed-off-by: Ildar Ismagilov <devix84@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Ildar Ismagilov 2018-01-31 22:39:53 +03:00 committed by Paul E. McKenney
parent cb4081cd4e
commit a35d13ec36
1 changed files with 3 additions and 0 deletions
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3
kernel/rcu/srcutree.c
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@ -579,6 +579,9 @@ static void srcu_gp_end(struct srcu_struct *sp)
if (ULONG_CMP_GE(gpseq,
sdp->srcu_gp_seq_needed + 100))
sdp->srcu_gp_seq_needed = gpseq;
if (ULONG_CMP_GE(gpseq,
sdp->srcu_gp_seq_needed_exp + 100))
sdp->srcu_gp_seq_needed_exp = gpseq;
spin_unlock_irqrestore_rcu_node(sdp, flags);
}
}