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eventfd - allow atomic read and waitqueue remove

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KVM needs a wait to atomically remove themselves from the eventfd ->poll()
wait queue head, in order to handle correctly their IRQfd deassign
operation.

This patch introduces such API, plus a way to read an eventfd from its
context.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Davide Libenzi
2010-01-13 09:34:36 -08:00
committed by Marcelo Tosatti
parent a6085fbaf6
commit cb289d6244
2 changed files with 90 additions and 15 deletions
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16
include/linux/eventfd.h
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@@ -10,6 +10,7 @@
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/wait.h>
/*
* CAREFUL: Check include/asm-generic/fcntl.h when defining
@@ -34,6 +35,9 @@ struct file *eventfd_fget(int fd);
struct eventfd_ctx *eventfd_ctx_fdget(int fd);
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file);
int eventfd_signal(struct eventfd_ctx *ctx, int n);
ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt);
int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,
__u64 *cnt);
#else /* CONFIG_EVENTFD */
@@ -61,6 +65,18 @@ static inline void eventfd_ctx_put(struct eventfd_ctx *ctx)
}
static inline ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait,
__u64 *cnt)
{
return -ENOSYS;
}
static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx,
wait_queue_t *wait, __u64 *cnt)
{
return -ENOSYS;
}
#endif
#endif /* _LINUX_EVENTFD_H */