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>

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>
Ashutosh Dixit · Greg Kroah-Hartman
1 parent 9420b3485a
Showing 1 changed file with 6 additions and 0 deletions Side-by-side Diff
Documentation/mic/mpssd/mpssd.c
@@ -1412,6 +1412,12 @@
 	}
  
 	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",
...	...	@@ -1412,6 +1412,12 @@
1412	1412	}
1413	1413
1414	1414	do {
	1415	+ ret = lseek(fd, 0, SEEK_SET);
	1416	+ if (ret < 0) {
	1417	+ mpsslog("%s: Failed to seek to file start '%s': %s\n",
	1418	+ mic->name, pathname, strerror(errno));
	1419	+ goto close_error1;
	1420	+ }
1415	1421	ret = read(fd, value, sizeof(value));
1416	1422	if (ret < 0) {
1417	1423	mpsslog("%s: Failed to read sysfs entry '%s': %s\n",