[libvirt] [PATCH v4 6/7] util: Introduce virFileWaitForExists
Since we have a number of places where we workaround timing issues with
devices, attributes (files in general) not being available at the time
of processing them by calling usleep in a loop for a fixed number of
tries, we could as well have a utility function that would do that.
Therefore we won't have to duplicate this ugly workaround even more.
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/libvirt_private.syms | 1 +
src/util/virfile.c | 31 +++++++++++++++++++++++++++++++
src/util/virfile.h | 2 ++
3 files changed, 34 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index d12db9b3f..57a5ea300 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1730,6 +1730,7 @@ virFileStripSuffix;
virFileTouch;
virFileUnlock;
virFileUpdatePerm;
+virFileWaitForExists;
virFileWrapperFdClose;
virFileWrapperFdFree;
virFileWrapperFdNew;
diff --git a/src/util/virfile.c b/src/util/virfile.c
index 2f28e83f4..01cc61e98 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -4166,3 +4166,34 @@ virFileReadValueString(char **value, const char *format, ...)
VIR_FREE(str);
return ret;
}
+
+
+/**
+ * virFileWaitForExists:
+ * @path: absolute path to a sysfs attribute (can be a symlink)
+ * @ms: how long to wait (in milliseconds)
+ * @tries: how many times should we try to wait for @path to become accessible
+ *
+ * Checks the existence of @path. In case the file defined by @path
+ * doesn't exist, we wait for it to appear in @ms milliseconds (for up to
+ * @tries attempts).
+ *
+ * Returns 0 on success, -1 on error, setting errno appropriately.
+ */
+int
+virFileWaitForExists(const char *path,
+ size_t ms,
+ size_t tries)
+{
+ errno = 0;
+
+ /* wait for @path to be accessible in @ms milliseconds, up to @tries */
+ while (tries-- > 0 && !virFileExists(path)) {
+ if (tries == 0 || errno != ENOENT)
+ return -1;
+
+ usleep(ms * 1000);
+ }
+
+ return 0;
+}
diff --git a/src/util/virfile.h b/src/util/virfile.h
index 57ceb8072..310a8e7f6 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -347,6 +347,8 @@ int virFileReadValueScaledInt(unsigned long long *value, const char
*format, ...
int virFileReadValueString(char **value, const char *format, ...)
ATTRIBUTE_FMT_PRINTF(2, 3);
+int virFileWaitForExists(const char *path, size_t ms, size_t tries);
+
int virFileInData(int fd,
int *inData,
--
2.13.5