misc: mic: Bug fix for sysfs poll usage.

MIC user space daemon poll's on sysfs changes. The documentation for
sysfs_poll(...) in fs/sysfs/file.c states that "Once poll/select
indicates that the value has changed, you need to close and re-open the
file, or seek to 0 and read again". This step was missed out earlier and
resulted in the daemon spinning continuously rather than getting blocked
in 'poll'. This bug was exposed by commit aea585ef8fa65163 introduced as
part of sysfs changes in 3.13-rc1. A seek to 0 has been introduced to
fix it.

Reviewed-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/mic/mpssd/mpssd.c b/Documentation/mic/mpssd/mpssd.c
index 0c980ad40b17be5c34a271c87c7983e112620d6b..5c7fdda56f0e148442d431ba0dfdf1f7c933b014 100644 (file)
--- a/Documentation/mic/mpssd/mpssd.c
+++ b/Documentation/mic/mpssd/mpssd.c
@@ -1412,6 +1412,12 @@ mic_config(void *arg)
        }
 
        do {
+               ret = lseek(fd, 0, SEEK_SET);
+               if (ret < 0) {
+                       mpsslog("%s: Failed to seek to file start '%s': %s\n",
+                               mic->name, pathname, strerror(errno));
+                       goto close_error1;
+               }
                ret = read(fd, value, sizeof(value));
                if (ret < 0) {
                        mpsslog("%s: Failed to read sysfs entry '%s': %s\n",