ACPI / OSL: Add IRQ handler flushing support in the OSL.
It is possible that a GPE handler or a fixed event handler still accessed after removing the handlers by invoking acpi_remove_gpe_handler() or acpi_remove_fixed_event_handler(), this possibility can crash OPSM after a module removal. In the Linux kernel, though all other GPE drivers are not modules, since the IPMI_SI (ipmi_si_intf.c) can be compiled as a module, we still need to consider a solution for this issue when the driver switches to ACPI_GPE_RAW_HANDLER mode in order to invoke GPE APIs. ACPICA expects acpi_os_wait_events_complete() to be invoked after GPE disabling so that OSPM can ensure all running GPE handlers have exitted. But currently acpi_os_wait_events_complete() can only flush _Lxx/_Exx evaluation work queue and this philosophy cannot work for drivers that have installed a dedicated GPE handler. The only way to protect a callback is to perform some state holders (reference count, state machine) before invoking the callback. Then this issue can only be fixed by the following means: 1. Flush GPE in ACPICA before invoking the GPE handler. But currently, there is no such implementation in acpi_ev_gpe_dispatch(). 2. Flush GPE in ACPICA OSL before invoking the SCI handler. But currently, there is no such implementation in acpi_irq(). 3. Flush IRQ in OSPM IRQ layer before invoking the IRQ handler. In Linus kernel, this can be done by synchronize_irq(). 4. Flush scheduling in OSPM vector entry layer before invoking the vector. In Linux, this can be done by synchronize_sched(). Since ACPICA expects the GPE handlers to be flushed by the ACPICA OSL or the GPE drivers. If it is implemented by the GPE driver, we should see synchronize_irq()/synchronize_sched() invoked in such drivers. If it is implemented by the ACPICA OSL, ACPICA currently provides acpi_os_wait_events_complete() hook to achieve this. After the following commit: Commit: 69c841b6 Author: Lv Zheng <lv.zheng@intel.com> Subject: ACPICA: Update use of acpi_os_wait_events_complete interface. The OSL acpi_os_wait_events_complete() is invoked after a GPE handler is removed from acpi_remove_gpe_handler() or a fixed event handler is removed from acpi_remove_fixed_event_handler(). Thus it is possible to implement GPE handler flushing using this ACPICA OSL now. So the solution 1 is currently not taken into account. By examining the IPMI_SI driver, we noticed that the IPMI_SI driver: 1. Uses free_irq() to flush non GPE based IRQ handlers, in free_irq(), synchronize_irq() is invoked, and 2. Uses acpi_remove_gpe_handler() to flush GPE based IRQ handlers, for such IRQ handlers, there is no synchronize_irq() invoked. Since there isn't synchronize_sched() implemented for this driver, from the driver's perspective, acpi_remove_gpe_handler() should have properly flushed the GPE handlers for it. Since the driver doesn't invoke synchronize_irq(), the solution 3 is not what the drivers expect. This patch implements solution 2. But since given the fact that the GPE is managed inside of ACPICA, and implementing the GPE flushing requires to implement the whole GPE management code again in the OSL, instead of flushing GPE, this patch flushes IRQ in acpi_os_wait_events_complete(). The flushing could last longer than expected as though the target GPE/fixed event that is removed can be fastly flushed, other GPEs/fix events can still be issued during the flushing period. This patch fixes this issue by invoking synchronize_hardirq() in acpi_os_wait_events_complete(). The reason why we don't invoke synchronize_irq() is: currently ACPICA is not threaded IRQ capable and the only difference between synchronize_irq() and synchronize_hardirq() is synchronize_irq() also flushes threaded IRQ handlers. Thus using synchronize_hardirq() can help to reduce the overall synchronization time for the current ACPICA implementation. Signed-off-by: Lv Zheng <lv.zheng@intel.com> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Len Brown <lenb@kernel.org> Cc: Robert Moore <robert.moore@intel.com> Cc: Corey Minyard <minyard@acm.org> Cc: linux-acpi@vger.kernel.org Cc: devel@acpica.org Cc: openipmi-developer@lists.sourceforge.net Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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