From b6dd4d83dc2f78cebc9a7e6e7e4bc2be4d29b94d Mon Sep 17 00:00:00 2001 From: Mark Salter Date: Fri, 2 Feb 2018 09:20:29 -0500 Subject: irqchip/gic-v3: Change pr_debug message to pr_devel The pr_debug() in gic-v3 gic_send_sgi() can trigger a circular locking warning: GICv3: CPU10: ICC_SGI1R_EL1 5000400 ====================================================== WARNING: possible circular locking dependency detected 4.15.0+ #1 Tainted: G W ------------------------------------------------------ dynamic_debug01/1873 is trying to acquire lock: ((console_sem).lock){-...}, at: [<0000000099c891ec>] down_trylock+0x20/0x4c but task is already holding lock: (&rq->lock){-.-.}, at: [<00000000842e1587>] __task_rq_lock+0x54/0xdc which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&rq->lock){-.-.}: __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock+0x4c/0x60 task_fork_fair+0x3c/0x148 sched_fork+0x10c/0x214 copy_process.isra.32.part.33+0x4e8/0x14f0 _do_fork+0xe8/0x78c kernel_thread+0x48/0x54 rest_init+0x34/0x2a4 start_kernel+0x45c/0x488 -> #1 (&p->pi_lock){-.-.}: __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 try_to_wake_up+0x48/0x600 wake_up_process+0x28/0x34 __up.isra.0+0x60/0x6c up+0x60/0x68 __up_console_sem+0x4c/0x7c console_unlock+0x328/0x634 vprintk_emit+0x25c/0x390 dev_vprintk_emit+0xc4/0x1fc dev_printk_emit+0x88/0xa8 __dev_printk+0x58/0x9c _dev_info+0x84/0xa8 usb_new_device+0x100/0x474 hub_port_connect+0x280/0x92c hub_event+0x740/0xa84 process_one_work+0x240/0x70c worker_thread+0x60/0x400 kthread+0x110/0x13c ret_from_fork+0x10/0x18 -> #0 ((console_sem).lock){-...}: validate_chain.isra.34+0x6e4/0xa20 __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 down_trylock+0x20/0x4c __down_trylock_console_sem+0x3c/0x9c console_trylock+0x20/0xb0 vprintk_emit+0x254/0x390 vprintk_default+0x58/0x90 vprintk_func+0xbc/0x164 printk+0x80/0xa0 __dynamic_pr_debug+0x84/0xac gic_raise_softirq+0x184/0x18c smp_cross_call+0xac/0x218 smp_send_reschedule+0x3c/0x48 resched_curr+0x60/0x9c check_preempt_curr+0x70/0xdc wake_up_new_task+0x310/0x470 _do_fork+0x188/0x78c SyS_clone+0x44/0x50 __sys_trace_return+0x0/0x4 other info that might help us debug this: Chain exists of: (console_sem).lock --> &p->pi_lock --> &rq->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&rq->lock); lock(&p->pi_lock); lock(&rq->lock); lock((console_sem).lock); *** DEADLOCK *** 2 locks held by dynamic_debug01/1873: #0: (&p->pi_lock){-.-.}, at: [<000000001366df53>] wake_up_new_task+0x40/0x470 #1: (&rq->lock){-.-.}, at: [<00000000842e1587>] __task_rq_lock+0x54/0xdc stack backtrace: CPU: 10 PID: 1873 Comm: dynamic_debug01 Tainted: G W 4.15.0+ #1 Hardware name: GIGABYTE R120-T34-00/MT30-GS2-00, BIOS T48 10/02/2017 Call trace: dump_backtrace+0x0/0x188 show_stack+0x24/0x2c dump_stack+0xa4/0xe0 print_circular_bug.isra.31+0x29c/0x2b8 check_prev_add.constprop.39+0x6c8/0x6dc validate_chain.isra.34+0x6e4/0xa20 __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 down_trylock+0x20/0x4c __down_trylock_console_sem+0x3c/0x9c console_trylock+0x20/0xb0 vprintk_emit+0x254/0x390 vprintk_default+0x58/0x90 vprintk_func+0xbc/0x164 printk+0x80/0xa0 __dynamic_pr_debug+0x84/0xac gic_raise_softirq+0x184/0x18c smp_cross_call+0xac/0x218 smp_send_reschedule+0x3c/0x48 resched_curr+0x60/0x9c check_preempt_curr+0x70/0xdc wake_up_new_task+0x310/0x470 _do_fork+0x188/0x78c SyS_clone+0x44/0x50 __sys_trace_return+0x0/0x4 GICv3: CPU0: ICC_SGI1R_EL1 12000 This could be fixed with printk_deferred() but that might lessen its usefulness for debugging. So change it to pr_devel to keep it out of production kernels. Developers working on gic-v3 can enable it as needed in their kernels. Signed-off-by: Mark Salter Signed-off-by: Marc Zyngier --- drivers/irqchip/irq-gic-v3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/irqchip/irq-gic-v3.c') diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index a57c0fbbd34a..d71be9a1f9d2 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -673,7 +673,7 @@ static void gic_send_sgi(u64 cluster_id, u16 tlist, unsigned int irq) MPIDR_TO_SGI_RS(cluster_id) | tlist << ICC_SGI1R_TARGET_LIST_SHIFT); - pr_debug("CPU%d: ICC_SGI1R_EL1 %llx\n", smp_processor_id(), val); + pr_devel("CPU%d: ICC_SGI1R_EL1 %llx\n", smp_processor_id(), val); gic_write_sgi1r(val); } -- cgit v1.2.3 From 21ec30c0ef5234fb1039cc7c7737d885bf875a9e Mon Sep 17 00:00:00 2001 From: Shanker Donthineni Date: Wed, 31 Jan 2018 18:03:42 -0600 Subject: irqchip/gic-v3: Use wmb() instead of smb_wmb() in gic_raise_softirq() A DMB instruction can be used to ensure the relative order of only memory accesses before and after the barrier. Since writes to system registers are not memory operations, barrier DMB is not sufficient for observability of memory accesses that occur before ICC_SGI1R_EL1 writes. A DSB instruction ensures that no instructions that appear in program order after the DSB instruction, can execute until the DSB instruction has completed. Cc: stable@vger.kernel.org Acked-by: Will Deacon , Signed-off-by: Shanker Donthineni Signed-off-by: Marc Zyngier --- drivers/irqchip/irq-gic-v3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/irqchip/irq-gic-v3.c') diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index d71be9a1f9d2..d99cc07903ec 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -688,7 +688,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) * Ensure that stores to Normal memory are visible to the * other CPUs before issuing the IPI. */ - smp_wmb(); + wmb(); for_each_cpu(cpu, mask) { u64 cluster_id = MPIDR_TO_SGI_CLUSTER_ID(cpu_logical_map(cpu)); -- cgit v1.2.3