diff options
| author | Vineet Gupta <vgupta@synopsys.com> | 2016-02-23 11:55:16 +0530 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2016-02-24 11:07:28 +0530 |
| commit | bb143f814ea488769ca2e79e0b376139cb5f134b (patch) | |
| tree | 32857f21fd6b8a9a4ae8457142c34260628c535e /arch/arc/kernel/mcip.c | |
| parent | 3e5177c1919bdc7651b5056f35409d0b4d728841 (diff) | |
ARCv2: SMP: Emulate IPI to self using software triggered interrupt
ARConnect/MCIP Inter-Core-Interrupt module can't send interrupt to
local core. So use core intc capability to trigger software
interrupt to self, using an unsued IRQ #21.
This showed up as csd deadlock with LTP trace_sched on a dual core
system. This test acts as scheduler fuzzer, triggering all sorts of
schedulting activity. Trouble starts with IPI to self, which doesn't get
delivered (effectively lost due to H/w capability), but the msg intended
to be sent remain enqueued in per-cpu @ipi_data.
All subsequent IPIs to this core from other cores get elided due to the
IPI coalescing optimization in ipi_send_msg_one() where a pending msg
implies an IPI already sent and assumes other core is yet to ack it.
After the elided IPI, other core simply goes into csd_lock_wait()
but never comes out as this core never sees the interrupt.
Fixes STAR 9001008624
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org> [4.2]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc/kernel/mcip.c')
| -rw-r--r-- | arch/arc/kernel/mcip.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c index 002c5fcf8947..9e1bd03b87a6 100644 --- a/arch/arc/kernel/mcip.c +++ b/arch/arc/kernel/mcip.c @@ -11,9 +11,12 @@ #include <linux/smp.h> #include <linux/irq.h> #include <linux/spinlock.h> +#include <asm/irqflags-arcv2.h> #include <asm/mcip.h> #include <asm/setup.h> +#define SOFTIRQ_IRQ 21 + static char smp_cpuinfo_buf[128]; static int idu_detected; @@ -22,6 +25,7 @@ static DEFINE_RAW_SPINLOCK(mcip_lock); static void mcip_setup_per_cpu(int cpu) { smp_ipi_irq_setup(cpu, IPI_IRQ); + smp_ipi_irq_setup(cpu, SOFTIRQ_IRQ); } static void mcip_ipi_send(int cpu) @@ -29,6 +33,12 @@ static void mcip_ipi_send(int cpu) unsigned long flags; int ipi_was_pending; + /* ARConnect can only send IPI to others */ + if (unlikely(cpu == raw_smp_processor_id())) { + arc_softirq_trigger(SOFTIRQ_IRQ); + return; + } + /* * NOTE: We must spin here if the other cpu hasn't yet * serviced a previous message. This can burn lots @@ -63,6 +73,11 @@ static void mcip_ipi_clear(int irq) unsigned long flags; unsigned int __maybe_unused copy; + if (unlikely(irq == SOFTIRQ_IRQ)) { + arc_softirq_clear(irq); + return; + } + raw_spin_lock_irqsave(&mcip_lock, flags); /* Who sent the IPI */ |