From 7c74d2bc5a9d43d33d6f16c1e706147162e2bc52 Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Fri, 12 Aug 2011 01:11:37 +0200 Subject: cpupower: Better detect offlined CPUs Before, checking for offlined CPUs was done dirty and it was checked whether topology parsing returned -1 values. But this is a valid case on a Xen (and possibly other) kernels. Do proper online/offline checking, also take CONFIG_HOTPLUG_CPU option into account (no /sys/devices/../cpuX/online file). Signed-off-by: Thomas Renninger Signed-off-by: Dominik Brodowski --- tools/power/cpupower/utils/helpers/sysfs.c | 50 ++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) (limited to 'tools/power/cpupower/utils/helpers/sysfs.c') diff --git a/tools/power/cpupower/utils/helpers/sysfs.c b/tools/power/cpupower/utils/helpers/sysfs.c index 55e2466674c6..c6343024a611 100644 --- a/tools/power/cpupower/utils/helpers/sysfs.c +++ b/tools/power/cpupower/utils/helpers/sysfs.c @@ -56,6 +56,56 @@ static unsigned int sysfs_write_file(const char *path, return (unsigned int) numwrite; } +/* + * Detect whether a CPU is online + * + * Returns: + * 1 -> if CPU is online + * 0 -> if CPU is offline + * negative errno values in error case + */ +int sysfs_is_cpu_online(unsigned int cpu) +{ + char path[SYSFS_PATH_MAX]; + int fd; + ssize_t numread; + unsigned long long value; + char linebuf[MAX_LINE_LEN]; + char *endp; + struct stat statbuf; + + snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u", cpu); + + if (stat(path, &statbuf) != 0) + return 0; + + /* + * kernel without CONFIG_HOTPLUG_CPU + * -> cpuX directory exists, but not cpuX/online file + */ + snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/online", cpu); + if (stat(path, &statbuf) != 0) + return 1; + + fd = open(path, O_RDONLY); + if (fd == -1) + return -errno; + + numread = read(fd, linebuf, MAX_LINE_LEN - 1); + if (numread < 1) { + close(fd); + return -EIO; + } + linebuf[numread] = '\0'; + close(fd); + + value = strtoull(linebuf, &endp, 0); + if (value > 1 || value < 0) + return -EINVAL; + + return value; +} + /* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */ /* -- cgit v1.2.2