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Subject[PATCH] RCU: Remove have_rcu_nocb_mask from tree_plugin.h
Date
Currently have_rcu_nocb_mask is used to avoid double allocation of
rcu_nocb_mask during boot up. Due to different representation of
cpumask_var_t on different kernel config CPUMASK=y(or n) it was okay.
But now we have a helper cpumask_available(), which can be utilized
to check whether rcu_nocb_mask has been allocated or not without using
a variable.

Removing the variable also reduces vmlinux size.

Unpatched version:
text data bss dec hex filename
13050393 7852470 14543408 35446271 21cddff vmlinux

Patched version:
text data bss dec hex filename
13050390 7852438 14543408 35446236 21cdddc vmlinux

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
---
Patch applied on top of linus's tree (commit cf9b0772f2e41).

kernel/rcu/tree_plugin.h | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index db85ca3..13a8e08 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -61,7 +61,6 @@ DEFINE_PER_CPU(char, rcu_cpu_has_work);

#ifdef CONFIG_RCU_NOCB_CPU
static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
-static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */
static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */

@@ -1752,7 +1751,6 @@ static void increment_cpu_stall_ticks(void)
static int __init rcu_nocb_setup(char *str)
{
alloc_bootmem_cpumask_var(&rcu_nocb_mask);
- have_rcu_nocb_mask = true;
cpulist_parse(str, rcu_nocb_mask);
return 1;
}
@@ -1801,7 +1799,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
/* Is the specified CPU a no-CBs CPU? */
bool rcu_is_nocb_cpu(int cpu)
{
- if (have_rcu_nocb_mask)
+ if (cpumask_available(rcu_nocb_mask))
return cpumask_test_cpu(cpu, rcu_nocb_mask);
return false;
}
@@ -2295,14 +2293,13 @@ void __init rcu_init_nohz(void)
need_rcu_nocb_mask = true;
#endif /* #if defined(CONFIG_NO_HZ_FULL) */

- if (!have_rcu_nocb_mask && need_rcu_nocb_mask) {
+ if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
return;
}
- have_rcu_nocb_mask = true;
}
- if (!have_rcu_nocb_mask)
+ if (!cpumask_available(rcu_nocb_mask))
return;

#if defined(CONFIG_NO_HZ_FULL)
@@ -2428,7 +2425,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp)
struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */
struct rcu_data *rdp_prev = NULL;

- if (!have_rcu_nocb_mask)
+ if (!cpumask_available(rcu_nocb_mask))
return;
if (ls == -1) {
ls = int_sqrt(nr_cpu_ids);
--
2.9.3
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