On Tue, Aug 05, 2014 at 01:37:47PM +0800, Wei.Yang@xxxxxxxxxxxxx wrote: > From: Yang Wei <Wei.Yang@xxxxxxxxxxxxx> > > In RT kernel, I ran into the following calltrace, so PMU interrupts cannot > be threaded > > in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/0 > INFO: lockdep is turned off. > Call Trace: > [<ffffffff8088595c>] dump_stack+0x1c/0x50 > [<ffffffff801a958c>] __might_sleep+0x13c/0x148 > [<ffffffff80891c54>] rt_spin_lock+0x3c/0xb0 > [<ffffffff801ad29c>] __wake_up+0x3c/0x80 > [<ffffffff80243ba4>] perf_event_wakeup+0x8c/0xf8 > [<ffffffff80243c50>] perf_pending_event+0x40/0x78 > [<ffffffff8023d88c>] irq_work_run+0x74/0xc0 > [<ffffffff80152640>] mipsxx_pmu_handle_shared_irq+0x110/0x228 > [<ffffffff8015276c>] mipsxx_pmu_handle_irq+0x14/0x30 > [<ffffffff801ffda4>] handle_irq_event_percpu+0xbc/0x470 > [<ffffffff80204478>] handle_percpu_irq+0x98/0xc8 > [<ffffffff801ff284>] generic_handle_irq+0x4c/0x68 > [<ffffffff8089748c>] do_IRQ+0x2c/0x48 > [<ffffffff80105864>] plat_irq_dispatch+0x64/0xd0 Hm... I don't see why based on this backtrace you concluce the handler needs to be marked IRQF_NO_THREAD. However there's another reason to mark it IRQF_NO_THREAD. IRQ threads may be rescheduled to other CPUs but this handler is fiddling with per-CPU resources. See https://patchwork.linux-mips.org/patch/2818/ for a similar scenario a few years ago. Ralf
