[Bug 220096][PATCH] acpi_thermal: Fix a possible sleep-under-mutex bug in acpi_tz_thread

[Jia-Ju Bai]

The driver may sleep under a mutex, and the code path is:
acpi_tz_thread [line 992: acquire the mutex]
acpi_tz_thread [line 993]
acpi_tz_thread [line 1003]
acpi_tz_thread [line 1004] (msleep is excuted)
acpi_tz_thread [line 1008]
acpi_tz_thread [line 970]
acpi_tz_thread [line 971]
acpi_tz_thread [line 975]
   malloc(M_WAITOK) [line 976]

The possible fix of this bug is to replace "M_WAITOK" in malloc with 
"M_NOWAIT".

This bug is found by a static analysis tool written by myself, and it is 
checked by my review of the FreeBSD code.

Signed-off-by: Jia-Ju Bai <baijiaju1990 at 163.com>
---
 sys/dev/acpica/acpi_thermal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/dev/acpica/acpi_thermal.c b/sys/dev/acpica/acpi_thermal.c
index b2b2a13aa88..fb9f44b5711 100644
--- a/sys/dev/acpica/acpi_thermal.c
+++ b/sys/dev/acpica/acpi_thermal.c
@@ -974,7 +974,7 @@ acpi_tz_thread(void *arg)
 	    }
 	    devclass_get_devices(acpi_tz_devclass, &devs, &devcount);
 	    sc = malloc(sizeof(struct acpi_tz_softc *) * devcount, M_TEMP,
-			M_WAITOK | M_ZERO);
+			M_NOWAIT | M_ZERO);
 	    for (i = 0; i < devcount; i++)
 		sc[i] = device_get_softc(devs[i]);
 	}
-- 
2.13.0