| Message ID | 20250620-temp-v3-1-6becc6aeb66c@chromium.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] thermal: sysfs: Return ENODATA instead of EAGAIN for reads | expand |
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c index 24b9055a0b6c515b865e0d7e2db1d0de176ff767..d80612506a334ab739e7545cdfe984ab4dffab7c 100644 --- a/drivers/thermal/thermal_sysfs.c +++ b/drivers/thermal/thermal_sysfs.c @@ -40,10 +40,13 @@ temp_show(struct device *dev, struct device_attribute *attr, char *buf) ret = thermal_zone_get_temp(tz, &temperature); - if (ret) - return ret; + if (!ret) + return sprintf(buf, "%d\n", temperature); - return sprintf(buf, "%d\n", temperature); + if (ret == -EAGAIN) + return -ENODATA; + + return ret; } static ssize_t
According to POSIX spec, EAGAIN returned by read with O_NONBLOCK set means the read would block. Hence, the common implementation in nonblocking model will poll the file when the nonblocking read returns EAGAIN. However, when the target file is thermal zone, this mechanism will totally malfunction because thermal zone doesn't implement sysfs notification and thus the poll will never return. For example, the read in Golang implemnts such method and sometimes hangs at reading some thermal zones via sysfs. Change to throw ENODATA instead of EAGAIN to userspace. Signed-off-by: Hsin-Te Yuan <yuanhsinte@chromium.org> --- Changes in v3: - Refine the control flow and optimize the success case. - Link to v2: https://lore.kernel.org/r/20250512-temp-v2-1-048be58eaaa5@chromium.org Changes in v2: - Modify commit message to make it clear - Link to v1: https://lore.kernel.org/r/20250409-temp-v1-1-9a391d8c60fd@chromium.org --- drivers/thermal/thermal_sysfs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- base-commit: 75f5f23f8787c5e184fcb2fbcd02d8e9317dc5e7 change-id: 20250409-temp-6ebd13ad0dbd Best regards,