Messages in this thread | | | Date | Wed, 17 Feb 2010 16:30:39 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH tip/core/rcu 17/18] rcu: stop overflowing signed integers |
| |
* Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > 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. > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
I had to do something similar for liburcu QSBR to follow the standard.
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> --- > 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 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; > } > diff --git a/kernel/rcutree.h b/kernel/rcutree.h > index d9d032a..7495fed 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 9d2c884..d45db2e 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; > } > -- > 1.6.6 >
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
| |