From: Sebastian Andrzej Siewior 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-4.19.1-rt3.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 --- 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 #include #include +#include #include "rcu.h" #include "rcu_segcblist.h" @@ -758,6 +759,8 @@ 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; @@ -766,13 +769,13 @@ 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. @@ -850,7 +853,7 @@ 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); @@ -866,7 +869,8 @@ 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)