From aa6083ed50957f699596999affbb6eb9d7a8b72e Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Fri, 7 Nov 2014 10:45:28 +0530 Subject: [PATCH] ARCv2: SMP: ARConnect debug/robustness - Handle possible interrupt coalescing from MCIP - chk if prev IPI ack before sending new Signed-off-by: Vineet Gupta --- arch/arc/Kconfig | 15 ++++++++++--- arch/arc/kernel/mcip.c | 48 ++++++++++++++++++++++++++++++++++++++---- arch/arc/kernel/smp.c | 20 ++++++++++++++---- 3 files changed, 72 insertions(+), 11 deletions(-) diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 301525020af7..ef5ca5969eaf 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -448,9 +448,10 @@ menuconfig ARC_DBG bool "ARC debugging" default y +if ARC_DBG + config ARC_DW2_UNWIND bool "Enable DWARF specific kernel stack unwind" - depends on ARC_DBG default y select KALLSYMS help @@ -464,18 +465,26 @@ config ARC_DW2_UNWIND config ARC_DBG_TLB_PARANOIA bool "Paranoia Checks in Low Level TLB Handlers" - depends on ARC_DBG default n config ARC_DBG_TLB_MISS_COUNT bool "Profile TLB Misses" default n select DEBUG_FS - depends on ARC_DBG help Counts number of I and D TLB Misses and exports them via Debugfs The counters can be cleared via Debugfs as well +if SMP + +config ARC_IPI_DBG + bool "Debug Inter Core interrupts" + default n + +endif + +endif + config ARC_UBOOT_SUPPORT bool "Support uboot arg Handling" default n diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c index e6ad6e64440a..35921c3ab394 100644 --- a/arch/arc/kernel/mcip.c +++ b/arch/arc/kernel/mcip.c @@ -33,27 +33,67 @@ void mcip_init_smp(unsigned int cpu) static void mcip_ipi_send(int cpu) { unsigned long flags; + int ipi_was_pending; + + /* + * NOTE: We must spin here if the other cpu hasn't yet + * serviced a previous message. This can burn lots + * of time, but we MUST follows this protocol or + * ipi messages can be lost!!! + * Also, we must release the lock in this loop because + * the other side may get to this same loop and not + * be able to ack -- thus causing deadlock. + */ + + do { + raw_spin_lock_irqsave(&mcip_lock, flags); + __mcip_cmd(CMD_INTRPT_READ_STATUS, cpu); + ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK); + if (ipi_was_pending == 0) + break; /* break out but keep lock */ + raw_spin_unlock_irqrestore(&mcip_lock, flags); + } while (1); - raw_spin_lock_irqsave(&mcip_lock, flags); __mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu); raw_spin_unlock_irqrestore(&mcip_lock, flags); + +#ifdef CONFIG_ARC_IPI_DBG + if (ipi_was_pending) + pr_info("IPI ACK delayed from cpu %d\n", cpu); +#endif } static void mcip_ipi_clear(int irq) { - unsigned int cpu; + unsigned int cpu, c; unsigned long flags; + unsigned int __maybe_unused copy; raw_spin_lock_irqsave(&mcip_lock, flags); /* Who sent the IPI */ __mcip_cmd(CMD_INTRPT_CHECK_SOURCE, 0); - cpu = read_aux_reg(ARC_REG_MCIP_READBACK); /* 1,2,4,8... */ + copy = cpu = read_aux_reg(ARC_REG_MCIP_READBACK); /* 1,2,4,8... */ - __mcip_cmd(CMD_INTRPT_GENERATE_ACK, __ffs(cpu)); /* 0,1,2,3... */ + /* + * In rare case, multiple concurrent IPIs sent to same target can + * possibly be coalesced by MCIP into 1 asserted IRQ, so @cpus can be + * "vectored" (multiple bits sets) as opposed to typical single bit + */ + do { + c = __ffs(cpu); /* 0,1,2,3 */ + __mcip_cmd(CMD_INTRPT_GENERATE_ACK, c); + cpu &= ~(1U << c); + } while (cpu); raw_spin_unlock_irqrestore(&mcip_lock, flags); + +#ifdef CONFIG_ARC_IPI_DBG + if (c != __ffs(copy)) + pr_info("IPIs from %x coalesced to %x\n", + copy, raw_smp_processor_id()); +#endif } volatile int wake_flag; diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c index d07cb53d7641..be13d12420ba 100644 --- a/arch/arc/kernel/smp.c +++ b/arch/arc/kernel/smp.c @@ -278,8 +278,10 @@ static void ipi_cpu_stop(void) machine_halt(); } -static inline void __do_IPI(unsigned long msg) +static inline int __do_IPI(unsigned long msg) { + int rc = 0; + switch (msg) { case IPI_RESCHEDULE: scheduler_ipi(); @@ -294,8 +296,10 @@ static inline void __do_IPI(unsigned long msg) break; default: - pr_warn("IPI with unexpected msg %ld\n", msg); + rc = 1; } + + return rc; } /* @@ -305,6 +309,7 @@ static inline void __do_IPI(unsigned long msg) irqreturn_t do_IPI(int irq, void *dev_id) { unsigned long pending; + unsigned long __maybe_unused copy; pr_debug("IPI [%ld] received on cpu %d\n", *this_cpu_ptr(&ipi_data), smp_processor_id()); @@ -316,11 +321,18 @@ irqreturn_t do_IPI(int irq, void *dev_id) * "dequeue" the msg corresponding to this IPI (and possibly other * piggybacked msg from elided IPIs: see ipi_send_msg_one() above) */ - pending = xchg(this_cpu_ptr(&ipi_data), 0); + copy = pending = xchg(this_cpu_ptr(&ipi_data), 0); do { unsigned long msg = __ffs(pending); - __do_IPI(msg); + int rc; + + rc = __do_IPI(msg); +#ifdef CONFIG_ARC_IPI_DBG + /* IPI received but no valid @msg */ + if (rc) + pr_info("IPI with bogus msg %ld in %ld\n", msg, copy); +#endif pending &= ~(1U << msg); } while (pending); -- 2.30.2