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c663600584
Booting a 3.2, 3.3, or 3.4-rc4 kernel on an Atari using the `nfeth' ethernet device triggers a WARN_ONCE() in generic irq handling code on the first irq for that device: WARNING: at kernel/irq/handle.c:146 handle_irq_event_percpu+0x134/0x142() irq 3 handler nfeth_interrupt+0x0/0x194 enabled interrupts Modules linked in: Call Trace: [<000299b2>] warn_slowpath_common+0x48/0x6a [<000299c0>] warn_slowpath_common+0x56/0x6a [<00029a4c>] warn_slowpath_fmt+0x2a/0x32 [<0005b34c>] handle_irq_event_percpu+0x134/0x142 [<0005b34c>] handle_irq_event_percpu+0x134/0x142 [<0000a584>] nfeth_interrupt+0x0/0x194 [<001ba0a8>] schedule_preempt_disabled+0x0/0xc [<0005b37a>] handle_irq_event+0x20/0x2c [<0005add4>] generic_handle_irq+0x2c/0x3a [<00002ab6>] do_IRQ+0x20/0x32 [<0000289e>] auto_irqhandler_fixup+0x4/0x6 [<00003144>] cpu_idle+0x22/0x2e [<001b8a78>] printk+0x0/0x18 [<0024d112>] start_kernel+0x37a/0x386 [<0003021d>] __do_proc_dointvec+0xb1/0x366 [<0003021d>] __do_proc_dointvec+0xb1/0x366 [<0024c31e>] _sinittext+0x31e/0x9c0 After invoking the irq's handler the kernel sees !irqs_disabled() and concludes that the handler erroneously enabled interrupts. However, debugging shows that !irqs_disabled() is true even before the handler is invoked, which indicates a problem in the platform code rather than the specific driver. The warning does not occur in 3.1 or older kernels. It turns out that the ALLOWINT definition for Atari is incorrect. The Atari definition of ALLOWINT is ~0x400, the stated purpose of that is to avoid taking HSYNC interrupts. irqs_disabled() returns true if the 3-bit ipl & 4 is non-zero. The nfeth interrupt runs at ipl 3 (it's autovector 3), but 3 & 4 is zero so irqs_disabled() is false, and the warning above is generated. When interrupts are explicitly disabled, ipl is set to 7. When they are enabled, ipl is masked with ALLOWINT. On Atari this will result in ipl = 3, which blocks interrupts at ipl 3 and below. So how come nfeth interrupts at ipl 3 are received at all? That's because ipl is reset to 2 by Atari-specific code in default_idle(), again with the stated purpose of blocking HSYNC interrupts. This discrepancy means that ipl 3 can remain blocked for longer than intended. Both default_idle() and falcon_hblhandler() identify HSYNC with ipl 2, and the "Atari ST/.../F030 Hardware Register Listing" agrees, but ALLOWINT is defined as if HSYNC was ipl 3. [As an experiment I modified default_idle() to reset ipl to 3, and as expected that resulted in all nfeth interrupts being blocked.] The fix is simple: define ALLOWINT as ~0x500 instead. This makes arch_local_irq_enable() consistent with default_idle(), and prevents the !irqs_disabled() problems for ipl 3 interrupts. Tested on Atari running in an Aranym VM. Signed-off-by: Mikael Pettersson <mikpe@it.uu.se> Tested-by: Michael Schmitz <schmitzmic@googlemail.com> (on Falcon/CT60) Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> |
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