de16dfcc51
[ Upstream commit b6dd4d83dc2f78cebc9a7e6e7e4bc2be4d29b94d ] 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 <msalter@redhat.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.