From 2a1021fce85cb9867f3655c58a9c826a3612fae9 Mon Sep 17 00:00:00 2001 From: Noam Camus Date: Tue, 9 Jun 2015 14:05:50 +0300 Subject: [PATCH] ARC: rwlock: disable interrupts in !LLSC variant If we hold rwlock and interrupt occures we may end up spinning on it for ever during softirq. Note that this lock is an internal lock and since the lock is free to be used from any context, the lock needs to be IRQ-safe. 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 Acked-by: Peter Zijlstra --- arch/arc/include/asm/spinlock.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h index db8c59d1eaeb..800e7c430ca5 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 -- 2.20.1