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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/4.19/older/patches-4.19.15-rt12.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 | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -39,6 +39,7 @@
#include <linux/module.h>
#include <linux/srcu.h>
#include <linux/cpu.h>
+#include <linux/locallock.h>
#include "rcu.h"
#include "rcu_segcblist.h"
@@ -760,6 +761,8 @@ static void srcu_flip(struct srcu_struct
* negligible when amoritized over that time period, and the extra latency
* of a needlessly non-expedited grace period is similarly negligible.
*/
+static DEFINE_LOCAL_IRQ_LOCK(sp_llock);
+
static bool srcu_might_be_idle(struct srcu_struct *sp)
{
unsigned long curseq;
@@ -768,13 +771,13 @@ 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(sp->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.
@@ -852,7 +855,7 @@ void __call_srcu(struct srcu_struct *sp,
return;
}
rhp->func = func;
- local_irq_save(flags);
+ local_lock_irqsave(sp_llock, flags);
sdp = this_cpu_ptr(sp->sda);
spin_lock_rcu_node(sdp);
rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false);
@@ -868,7 +871,8 @@ void __call_srcu(struct srcu_struct *sp,
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(sp, sdp, s, do_norm);
else if (needexp)
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