From 20133cfce7d0bbdcc0c398301030c091f5675c88 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 22 Feb 2010 17:05:01 -0800 Subject: [PATCH] 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 Signed-off-by: Paul E. McKenney 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 --- kernel/rcutree.c | 11 +++++------ kernel/rcutree.h | 33 ++++++++++++++++++--------------- kernel/rcutree_trace.c | 14 +++++++------- 3 files changed, 30 insertions(+), 28 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 29d88c08d875..dd0d31dffcdc 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; } diff --git a/kernel/rcutree.h b/kernel/rcutree.h index d9d032abd665..7495fed49c30 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -92,10 +92,10 @@ struct rcu_dynticks { struct rcu_node { spinlock_t lock; /* Root rcu_node's lock protects some */ /* rcu_state fields as well as following. */ - long gpnum; /* Current grace period for this node. */ + unsigned long gpnum; /* Current grace period for this node. */ /* This will either be equal to or one */ /* behind the root rcu_node's gpnum. */ - long completed; /* Last grace period completed for this node. */ + unsigned long completed; /* Last GP completed for this node. */ /* This will either be equal to or one */ /* behind the root rcu_node's gpnum. */ unsigned long qsmask; /* CPUs or groups that need to switch in */ @@ -161,11 +161,11 @@ struct rcu_node { /* Per-CPU data for read-copy update. */ struct rcu_data { /* 1) quiescent-state and grace-period handling : */ - long completed; /* Track rsp->completed gp number */ + unsigned long completed; /* Track rsp->completed gp number */ /* in order to detect GP end. */ - long gpnum; /* Highest gp number that this CPU */ + unsigned long gpnum; /* Highest gp number that this CPU */ /* is aware of having started. */ - long passed_quiesc_completed; + unsigned long passed_quiesc_completed; /* Value of completed at time of qs. */ bool passed_quiesc; /* User-mode/idle loop etc. */ bool qs_pending; /* Core waits for quiesc state. */ @@ -221,14 +221,14 @@ struct rcu_data { unsigned long resched_ipi; /* Sent a resched IPI. */ /* 5) __rcu_pending() statistics. */ - long n_rcu_pending; /* rcu_pending() calls since boot. */ - long n_rp_qs_pending; - long n_rp_cb_ready; - long n_rp_cpu_needs_gp; - long n_rp_gp_completed; - long n_rp_gp_started; - long n_rp_need_fqs; - long n_rp_need_nothing; + unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ + unsigned long n_rp_qs_pending; + unsigned long n_rp_cb_ready; + unsigned long n_rp_cpu_needs_gp; + unsigned long n_rp_gp_completed; + unsigned long n_rp_gp_started; + unsigned long n_rp_need_fqs; + unsigned long n_rp_need_nothing; int cpu; }; @@ -255,6 +255,9 @@ struct rcu_data { #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ +#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) +#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) + /* * RCU global state, including node hierarchy. This hierarchy is * represented in "heap" form in a dense array. The root (first level) @@ -283,8 +286,8 @@ struct rcu_state { /* period because */ /* force_quiescent_state() */ /* was running. */ - long gpnum; /* Current gp number. */ - long completed; /* # of last completed gp. */ + unsigned long gpnum; /* Current gp number. */ + unsigned long completed; /* # of last completed gp. */ /* End of fields guarded by root rcu_node's lock. */ diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index 9d2c88423b31..d45db2e35d27 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -50,7 +50,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) return; - seq_printf(m, "%3d%cc=%ld g=%ld pq=%d pqc=%ld qp=%d", + seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pqc=%lu qp=%d", rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ', rdp->completed, rdp->gpnum, @@ -105,7 +105,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) return; - seq_printf(m, "%d,%s,%ld,%ld,%d,%ld,%d", + seq_printf(m, "%d,%s,%lu,%lu,%d,%lu,%d", rdp->cpu, cpu_is_offline(rdp->cpu) ? "\"N\"" : "\"Y\"", rdp->completed, rdp->gpnum, @@ -155,13 +155,13 @@ static const struct file_operations rcudata_csv_fops = { static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) { - long gpnum; + unsigned long gpnum; int level = 0; int phase; struct rcu_node *rnp; gpnum = rsp->gpnum; - seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x " + seq_printf(m, "c=%lu g=%lu s=%d jfq=%ld j=%x " "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld\n", rsp->completed, gpnum, rsp->signaled, (long)(rsp->jiffies_force_qs - jiffies), @@ -215,12 +215,12 @@ static const struct file_operations rcuhier_fops = { static int show_rcugp(struct seq_file *m, void *unused) { #ifdef CONFIG_TREE_PREEMPT_RCU - seq_printf(m, "rcu_preempt: completed=%ld gpnum=%ld\n", + seq_printf(m, "rcu_preempt: completed=%ld gpnum=%lu\n", rcu_preempt_state.completed, rcu_preempt_state.gpnum); #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ - seq_printf(m, "rcu_sched: completed=%ld gpnum=%ld\n", + seq_printf(m, "rcu_sched: completed=%ld gpnum=%lu\n", rcu_sched_state.completed, rcu_sched_state.gpnum); - seq_printf(m, "rcu_bh: completed=%ld gpnum=%ld\n", + seq_printf(m, "rcu_bh: completed=%ld gpnum=%lu\n", rcu_bh_state.completed, rcu_bh_state.gpnum); return 0; } -- 2.20.1