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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-02-22 17:05:01 -0800
committerIngo Molnar <mingo@elte.hu>2010-02-25 10:34:57 +0100
commit20133cfce7d0bbdcc0c398301030c091f5675c88 (patch)
tree337f242bfc89f5880cf86234fa6b574f52a2f0a5 /kernel/rcutree.c
parent1bd22e374b20c2f0ba1d2723c1f585acab2251c5 (diff)
downloadop-kernel-dev-20133cfce7d0bbdcc0c398301030c091f5675c88.zip
op-kernel-dev-20133cfce7d0bbdcc0c398301030c091f5675c88.tar.gz
rcu: Stop overflowing signed integers
The C standard does not specify the result of an operation that overflows a signed integer, so such operations need to be avoided. This patch changes the type of several fields from "long" to "unsigned long" and adjusts operations as needed. ULONG_CMP_GE() and ULONG_CMP_LT() macros are introduced to do the modular comparisons that are appropriate given that overflow is an expected event. Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-17-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 29d88c0..dd0d31d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -500,7 +500,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
trigger_all_cpu_backtrace();
spin_lock_irqsave(&rnp->lock, flags);
- if ((long)(jiffies - rsp->jiffies_stall) >= 0)
+ if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
rsp->jiffies_stall =
jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1216,8 +1216,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
return; /* Someone else is already on the job. */
}
- if (relaxed &&
- (long)(rsp->jiffies_force_qs - jiffies) >= 0)
+ if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
goto unlock_fqs_ret; /* no emergency and done recently. */
rsp->n_force_qs++;
spin_lock(&rnp->lock); /* irqs already disabled */
@@ -1295,7 +1294,7 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
* If an RCU GP has gone long enough, go check for dyntick
* idle CPUs and, if needed, send resched IPIs.
*/
- if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)
+ if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
force_quiescent_state(rsp, 1);
/*
@@ -1392,7 +1391,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
force_quiescent_state(rsp, 0);
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->qlen_last_fqs_check = rdp->qlen;
- } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)
+ } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
force_quiescent_state(rsp, 1);
local_irq_restore(flags);
}
@@ -1525,7 +1524,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
/* Has an RCU GP gone long enough to send resched IPIs &c? */
if (rcu_gp_in_progress(rsp) &&
- ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) {
+ ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
rdp->n_rp_need_fqs++;
return 1;
}
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