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Date: Sat, 31 Oct 2015 15:15:12 +0200
From: Noam Camus <noamc@...hip.com>
To: <linux-snps-arc@...ts.infradead.org>
CC: <linux-kernel@...r.kernel.org>, <talz@...hip.com>,
<gilf@...hip.com>, <cmetcalf@...hip.com>,
Noam Camus <noamc@...hip.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v1 05/20] ARC: rwlock: disable interrupts in !LLSC variant
From: Noam Camus <noamc@...hip.com>
If we hold rw->lock_mutex and interrupt occures we may
end up spinning on it for ever during softirq.
Below you may see an example for interrupt we get while
nl_table_lock is holding its rw->lock_mutex and we spinned
on it for ever.
The concept for the fix was taken from SPARC.
[2015-05-12 19:16:12] Stack Trace:
[2015-05-12 19:16:12] arc_unwind_core+0xb8/0x11c
[2015-05-12 19:16:12] dump_stack+0x68/0xac
[2015-05-12 19:16:12] _raw_read_lock+0xa8/0xac
[2015-05-12 19:16:12] netlink_broadcast_filtered+0x56/0x35c
[2015-05-12 19:16:12] nlmsg_notify+0x42/0xa4
[2015-05-12 19:16:13] neigh_update+0x1fe/0x44c
[2015-05-12 19:16:13] neigh_event_ns+0x40/0xa4
[2015-05-12 19:16:13] arp_process+0x46e/0x5a8
[2015-05-12 19:16:13] __netif_receive_skb_core+0x358/0x500
[2015-05-12 19:16:13] process_backlog+0x92/0x154
[2015-05-12 19:16:13] net_rx_action+0xb8/0x188
[2015-05-12 19:16:13] __do_softirq+0xda/0x1d8
[2015-05-12 19:16:14] irq_exit+0x8a/0x8c
[2015-05-12 19:16:14] arch_do_IRQ+0x6c/0xa8
[2015-05-12 19:16:14] handle_interrupt_level1+0xe4/0xf0
Signed-off-by: Noam Camus <noamc@...hip.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
arch/arc/include/asm/spinlock.h | 14 ++++++++++++++
1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
index db8c59d..800e7c4 100644
--- a/arch/arc/include/asm/spinlock.h
+++ b/arch/arc/include/asm/spinlock.h
@@ -610,7 +610,9 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
int ret = 0;
+ unsigned long flags;
+ local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
/*
@@ -623,6 +625,7 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
}
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
smp_mb();
return ret;
@@ -632,7 +635,9 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
int ret = 0;
+ unsigned long flags;
+ local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
/*
@@ -646,6 +651,7 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
ret = 1;
}
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
return ret;
}
@@ -664,16 +670,24 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
rw->counter++;
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
}
#endif
--
1.7.1
--
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