Don't exit with error when hwmon dir is removed

There is a race condition between when an hwmon
directory is removed and systemd halting the
phosphor-hwmon application monitoring it. This
code change ensures the application does not return
an error in these cases.

Resolves openbmc/openbmc#1789

Change-Id: If4f032759c522aa811d4092e7a7d8ea275480e4a
Signed-off-by: Andrew Geissler <andrewg@us.ibm.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/sysfs.cpp b/sysfs.cpp
index 3ca2ec4..bc94b12 100644
--- a/sysfs.cpp
+++ b/sysfs.cpp
@@ -180,6 +180,18 @@ int readSysfsWithCallout(const std::string& root,
         // errno should still reflect the error from the failing open
         // or read system calls that got us here.
         auto rc = errno;
+
+        // If the directory disappeared then this application should gracefully
+        // exit.  There are race conditions between the unloading of a hwmon
+        // driver and the stopping of this service by systemd.  To prevent
+        // this application from falsely failing in these scenarios, it will
+        // simply exit if the directory or file can not be found.  It is up
+        // to the user(s) of this provided hwmon object to log the appropriate
+        // errors if the object disappears when it should not.
+        if (rc == ENOENT)
+        {
+            exit(0);
+        }
         instancePath /= "device";
         using namespace sdbusplus::xyz::openbmc_project::Sensor::Device::Error;
         report<ReadFailure>(