diff options
Diffstat (limited to 'arch/um/kernel/irq.c')
| -rw-r--r-- | arch/um/kernel/irq.c | 131 |
1 files changed, 128 insertions, 3 deletions
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c index dbf2f5bc842f..dba04d88b432 100644 --- a/arch/um/kernel/irq.c +++ b/arch/um/kernel/irq.c @@ -1,4 +1,4 @@ -/* +/* * Copyright (C) 2000 Jeff Dike (jdike@karaya.com) * Licensed under the GPL * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c: @@ -25,7 +25,6 @@ #include "asm/system.h" #include "asm/errno.h" #include "asm/uaccess.h" -#include "user_util.h" #include "kern_util.h" #include "irq_user.h" #include "irq_kern.h" @@ -33,6 +32,7 @@ #include "sigio.h" #include "um_malloc.h" #include "misc_constants.h" +#include "as-layout.h" /* * Generic, controller-independent functions: @@ -54,7 +54,7 @@ int show_interrupts(struct seq_file *p, void *v) if (i < NR_IRQS) { spin_lock_irqsave(&irq_desc[i].lock, flags); action = irq_desc[i].action; - if (!action) + if (!action) goto skip; seq_printf(p, "%3d: ",i); #ifndef CONFIG_SMP @@ -79,6 +79,14 @@ skip: return 0; } +/* + * This list is accessed under irq_lock, except in sigio_handler, + * where it is safe from being modified. IRQ handlers won't change it - + * if an IRQ source has vanished, it will be freed by free_irqs just + * before returning from sigio_handler. That will process a separate + * list of irqs to free, with its own locking, coming back here to + * remove list elements, taking the irq_lock to do so. + */ static struct irq_fd *active_fds = NULL; static struct irq_fd **last_irq_ptr = &active_fds; @@ -244,6 +252,7 @@ void free_irq_by_fd(int fd) free_irq_by_cb(same_fd, &fd); } +/* Must be called with irq_lock held */ static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out) { struct irq_fd *irq; @@ -309,6 +318,12 @@ void deactivate_fd(int fd, int irqnum) ignore_sigio_fd(fd); } +/* + * Called just before shutdown in order to provide a clean exec + * environment in case the system is rebooting. No locking because + * that would cause a pointless shutdown hang if something hadn't + * released the lock. + */ int deactivate_all_fds(void) { struct irq_fd *irq; @@ -454,3 +469,113 @@ int init_aio_irq(int irq, char *name, irq_handler_t handler) out: return err; } + +/* + * IRQ stack entry and exit: + * + * Unlike i386, UML doesn't receive IRQs on the normal kernel stack + * and switch over to the IRQ stack after some preparation. We use + * sigaltstack to receive signals on a separate stack from the start. + * These two functions make sure the rest of the kernel won't be too + * upset by being on a different stack. The IRQ stack has a + * thread_info structure at the bottom so that current et al continue + * to work. + * + * to_irq_stack copies the current task's thread_info to the IRQ stack + * thread_info and sets the tasks's stack to point to the IRQ stack. + * + * from_irq_stack copies the thread_info struct back (flags may have + * been modified) and resets the task's stack pointer. + * + * Tricky bits - + * + * What happens when two signals race each other? UML doesn't block + * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal + * could arrive while a previous one is still setting up the + * thread_info. + * + * There are three cases - + * The first interrupt on the stack - sets up the thread_info and + * handles the interrupt + * A nested interrupt interrupting the copying of the thread_info - + * can't handle the interrupt, as the stack is in an unknown state + * A nested interrupt not interrupting the copying of the + * thread_info - doesn't do any setup, just handles the interrupt + * + * The first job is to figure out whether we interrupted stack setup. + * This is done by xchging the signal mask with thread_info->pending. + * If the value that comes back is zero, then there is no setup in + * progress, and the interrupt can be handled. If the value is + * non-zero, then there is stack setup in progress. In order to have + * the interrupt handled, we leave our signal in the mask, and it will + * be handled by the upper handler after it has set up the stack. + * + * Next is to figure out whether we are the outer handler or a nested + * one. As part of setting up the stack, thread_info->real_thread is + * set to non-NULL (and is reset to NULL on exit). This is the + * nesting indicator. If it is non-NULL, then the stack is already + * set up and the handler can run. + */ + +static unsigned long pending_mask; + +unsigned long to_irq_stack(int sig, unsigned long *mask_out) +{ + struct thread_info *ti; + unsigned long mask, old; + int nested; + + mask = xchg(&pending_mask, 1 << sig); + if(mask != 0){ + /* If any interrupts come in at this point, we want to + * make sure that their bits aren't lost by our + * putting our bit in. So, this loop accumulates bits + * until xchg returns the same value that we put in. + * When that happens, there were no new interrupts, + * and pending_mask contains a bit for each interrupt + * that came in. + */ + old = 1 << sig; + do { + old |= mask; + mask = xchg(&pending_mask, old); + } while(mask != old); + return 1; + } + + ti = current_thread_info(); + nested = (ti->real_thread != NULL); + if(!nested){ + struct task_struct *task; + struct thread_info *tti; + + task = cpu_tasks[ti->cpu].task; + tti = task_thread_info(task); + *ti = *tti; + ti->real_thread = tti; + task->stack = ti; + } + + mask = xchg(&pending_mask, 0); + *mask_out |= mask | nested; + return 0; +} + +unsigned long from_irq_stack(int nested) +{ + struct thread_info *ti, *to; + unsigned long mask; + + ti = current_thread_info(); + + pending_mask = 1; + + to = ti->real_thread; + current->stack = to; + ti->real_thread = NULL; + *to = *ti; + + mask = xchg(&pending_mask, 0); + return mask & ~1; +} + |