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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 12 Oct 2017 18:37:12 +0200
Subject: [PATCH] srcu: replace local_irqsave() with a locallock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.17-rt9.tar.xz
There are two instances which disable interrupts in order to become a
stable this_cpu_ptr() pointer. The restore part is coupled with
spin_unlock_irqrestore() which does not work on RT.
Replace the local_irq_save() call with the appropriate local_lock()
version of it.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/rcu/srcutree.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -25,6 +25,7 @@
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/srcu.h>
+#include <linux/locallock.h>
#include "rcu.h"
#include "rcu_segcblist.h"
@@ -735,6 +736,7 @@ static void srcu_flip(struct srcu_struct
smp_mb(); /* D */ /* Pairs with C. */
}
+static DEFINE_LOCAL_IRQ_LOCK(sp_llock);
/*
* If SRCU is likely idle, return true, otherwise return false.
*
@@ -764,13 +766,13 @@ static bool srcu_might_be_idle(struct sr
unsigned long t;
/* If the local srcu_data structure has callbacks, not idle. */
- local_irq_save(flags);
+ local_lock_irqsave(sp_llock, flags);
sdp = this_cpu_ptr(ssp->sda);
if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) {
- local_irq_restore(flags);
+ local_unlock_irqrestore(sp_llock, flags);
return false; /* Callbacks already present, so not idle. */
}
- local_irq_restore(flags);
+ local_unlock_irqrestore(sp_llock, flags);
/*
* No local callbacks, so probabalistically probe global state.
@@ -850,7 +852,7 @@ void __call_srcu(struct srcu_struct *ssp
}
rhp->func = func;
idx = srcu_read_lock(ssp);
- local_irq_save(flags);
+ local_lock_irqsave(sp_llock, flags);
sdp = this_cpu_ptr(ssp->sda);
spin_lock_rcu_node(sdp);
rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false);
@@ -866,7 +868,8 @@ void __call_srcu(struct srcu_struct *ssp
sdp->srcu_gp_seq_needed_exp = s;
needexp = true;
}
- spin_unlock_irqrestore_rcu_node(sdp, flags);
+ spin_unlock_rcu_node(sdp);
+ local_unlock_irqrestore(sp_llock, flags);
if (needgp)
srcu_funnel_gp_start(ssp, sdp, s, do_norm);
else if (needexp)
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