FDDI: defza: Sanitise the reset safety timer The reset actions of the DEFZA adapters are exceedingly slow, taking up to 30 seconds to complete by the device spec and typically in the range of 10 seconds in reality, as required for the device RTOS to boot, still quite a lot. Therefore a state machine is used that's interrupt driven, however a safety mechanism is required in case of adapter malfunction, so that if no state change interrupt has arrived in time, then the situation is taken care of. The safety mechanism depends on the origin of the reset. For regular adapter initialisation at the device probe time a sleep is requested. However a reset is also required by the device spec when the adapter has transitioned into the halted state, such as in response to a PC Trace event in the course of ring fault recovery, possibly a common network event. In that case no sleep is possible as a device halt is reported at the hardirq level. A timer is therefore set up to ensure progress in case no adapter state change interrupt has arrived in time, but as from commit 168f6b6ffbee ("timers: Use del_timer_sync() even on UP") a warning is issued as the timer is deleted in the hardirq handler upon an expected state change: defza: v.1.1.4 Oct 6 2018 Maciej W. Rozycki tc2: DEC FDDIcontroller 700 or 700-C at 0x18000000, irq 4 tc2: resetting the board... ------------[ cut here ]------------ WARNING: kernel/time/timer.c:1611 at __timer_delete_sync+0x104/0x120, CPU#0: swapper/0/0 Modules linked in: CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.0.0-dirty #2 VOLUNTARY Stack : 9800000002027d08 00000000140120e0 0000000000000000 ffffffff8089d468 0000000000000000 0000000000000000 ffffffff807ed6b8 ffffffff80897458 ffffffff80897400 9800000002027b88 0000000000000000 7070617773203a6d 0000000000000000 9800000002027ba4 0000000000001000 6465746e69617420 0000000000000000 ffffffff807ed6b8 00000000140120e0 0000000000000009 000000000000064b ffffffff800dd14c 0000000000000036 9800000002184000 0000000000000000 0000000000000020 0000000000000000 ffffffff80910000 ffffffff8085c000 9800000002027c70 0000000000000001 ffffffff80045fa0 0000000000000000 0000000000000000 0000000000000000 0000000000000009 000000000000064b ffffffff800502b8 ffffffff807ed6b8 ffffffff80045fa0 ... Call Trace: [] show_stack+0x28/0xf0 [] dump_stack_lvl+0x48/0x7c [] __warn+0xa0/0x128 [] warn_slowpath_fmt+0x64/0xa4 [] __timer_delete_sync+0x104/0x120 [] fza_interrupt+0xc74/0xeb8 [] __handle_irq_event_percpu+0x70/0x228 [] handle_irq_event_percpu+0x18/0x78 [] handle_percpu_irq+0x50/0x80 [] generic_handle_irq+0x90/0xd0 [] do_IRQ+0x1c/0x30 [] handle_int+0x148/0x154 [] do_idle+0x40/0x108 [] cpu_startup_entry+0x2c/0x38 [] kernel_init+0x0/0x108 ---[ end trace 0000000000000000 ]--- tc2: OK tc2: model 700 (DEFZA-AA), MMF PMD, address 08-00-2b-xx-xx-xx tc2: ROM rev. 1.0, firmware rev. 1.2, RMC rev. A, SMT ver. 1 tc2: link unavailable ------------[ cut here ]------------ WARNING: kernel/time/timer.c:1611 at __timer_delete_sync+0x104/0x120, CPU#0: swapper/0/0 Modules linked in: CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G W 7.0.0-dirty #2 VOLUNTARY Tainted: [W]=WARN Stack : 9800000002027d08 00000000140120e0 0000000000000000 ffffffff8089d468 0000000000000000 0000000000000000 ffffffff807ed6b8 ffffffff80897458 ffffffff80897400 9800000002027b88 0000000000000000 0000000000000000 0000000000000000 9800000002027ba4 0000000000001000 0000000000000000 0000000000000000 ffffffff807ed6b8 00000000140120e0 0000000000000009 000000000000064b ffffffff800dd14c 0000000000000036 9800000002184000 0000000000000000 0000000000000020 0000000000000000 ffffffff80910000 ffffffff8085c000 9800000002027c70 0000000000000001 ffffffff80045fa0 0000000000000000 0000000000000000 0000000000000000 0000000000000009 000000000000064b ffffffff800502b8 ffffffff807ed6b8 ffffffff80045fa0 ... Call Trace: [] show_stack+0x28/0xf0 [] dump_stack_lvl+0x48/0x7c [] __warn+0xa0/0x128 [] warn_slowpath_fmt+0x64/0xa4 [] __timer_delete_sync+0x104/0x120 [] fza_interrupt+0xc74/0xeb8 [] __handle_irq_event_percpu+0x70/0x228 [] handle_irq_event_percpu+0x18/0x78 [] handle_percpu_irq+0x50/0x80 [] generic_handle_irq+0x90/0xd0 [] do_IRQ+0x1c/0x30 [] handle_int+0x148/0x154 [] arch_local_irq_disable+0x4/0x28 [] do_idle+0x50/0x108 [] cpu_startup_entry+0x2c/0x38 [] kernel_init+0x0/0x108 ---[ end trace 0000000000000000 ]--- tc2: registered as fddi0 The immediate origin of the new warning is the switch away from aliasing del_timer_sync() to del_timer() (timer_delete_sync() to timer_delete() in terms of current function names) for UP configurations, which however is the only choice for this driver anyway as no SMP hardware supports the TURBOchannel bus this device interfaces to. Therefore there is a very remote issue only this is a sign of. Specifically if an adapter reset issued upon a transition to the halted state times out and first triggers fza_reset_timer() for another reset assertion, which then schedules fza_reset_timer() for reset deassertion and then that second call is pre-empted after poking at the hardware, but before the timer has been rearmed and owing to high system load causing exceedingly high scheduling latency control is not handed back before a transition to the uninitialised state has caused the timer to be deleted even before it has been started, then fza_reset_timer() will be called yet again and issue another reset even though by then the adapter has already recovered. Prevent this situation from happening by switching to timer_delete() for the transition to the halted state and protect the code region affected with a spinlock, also to make sure add_timer() has not been called twice in a row due to an execution race between the interrupt handler and the timer handler (though it could only happen on SMP, but let's keep the driver clean). It's a very unlikely sequence of events to happen and therefore there's no point in trying to be overly clever about it, such as by placing printk() calls outside the protection. For the transition to the uninitialised state switch to timer_delete_sync_try() instead, so that a timer isn't deleted that's just been rearmed by the timer handler and needs to watch for the device to come out of reset again (again, an SMP scenario only). Retain timer_delete_sync() invocations outside the hardirq context for a stray timer not to fire once device structures have been released. Fixes: 61414f5ec9834 ("FDDI: defza: Add support for DEC FDDIcontroller 700 TURBOchannel adapter") Signed-off-by: Maciej W. Rozycki Signed-off-by: Jakub Kicinski