Writing to dscr_default in sysfs doesn't actually change the DSCR - we rely on a context switch on each CPU to do the work. There is no guarantee we will get a context switch in a reasonable amount of time so fire off an IPI to force an immediate change.
This issue was found with the following test case: http://ozlabs.org/~anton/junkcode/dscr_explicit_test.c Signed-off-by: Anton Blanchard <an...@samba.org> Cc: <sta...@kernel.org> # 3.0+ --- Index: b/arch/powerpc/kernel/sysfs.c =================================================================== --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -194,6 +194,12 @@ static ssize_t show_dscr_default(struct return sprintf(buf, "%lx\n", dscr_default); } +static void update_dscr(void *dummy) +{ + if (!current->thread.dscr_inherit) + mtspr(SPRN_DSCR, dscr_default); +} + static ssize_t __used store_dscr_default(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) @@ -206,6 +212,8 @@ static ssize_t __used store_dscr_default return -EINVAL; dscr_default = val; + on_each_cpu(update_dscr, NULL, 1); + return count; } _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
