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rcu: Stop overflowing signed integers

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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>
This commit is contained in:
Paul E. McKenney
2010-02-22 17:05:01 -08:00
committed by Ingo Molnar
parent 1bd22e374b
commit 20133cfce7
3 changed files with 30 additions and 28 deletions
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33
kernel/rcutree.h
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@@ -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. */