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authorJeff Dike <jdike@addtoit.com>2007-05-06 14:51:27 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-07 12:13:02 -0700
commitd973a77bdb3ade9240173b6ed6e003a319499211 (patch)
tree66be056cdd213a89b85354c32b0f5ad6de703b21 /arch
parent1d1497e1f9ffe2f7198c916abd112226a7a503f2 (diff)
downloadlinux-2.6.34-ux500-d973a77bdb3ade9240173b6ed6e003a319499211.tar.gz
uml: irq locking commentary
Locking commentary. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/um/kernel/irq.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index a1e8c460b75..8f2ed369031 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -78,6 +78,14 @@ 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;
@@ -243,6 +251,7 @@ 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;
@@ -308,6 +317,12 @@ 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;