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authorAnton Blanchard <anton@samba.org>2012-09-03 16:48:46 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-12-17 10:49:05 -0800
commit3882a18f5fa8a707024ac599070f2298cfc2ff39 (patch)
tree9d17a711dbb971761af78acb06e40f0765aea6dd
parent1758e55fd05e042e873f6d54657552ee1730bb32 (diff)
powerpc: Keep thread.dscr and thread.dscr_inherit in sync
commit 00ca0de02f80924dfff6b4f630e1dff3db005e35 upstream. When we update the DSCR either via emulation of mtspr(DSCR) or via a change to dscr_default in sysfs we don't update thread.dscr. We will eventually update it at context switch time but there is a period where thread.dscr is incorrect. If we fork at this point we will copy the old value of thread.dscr into the child. To avoid this, always keep thread.dscr in sync with reality. This issue was found with the following testcase: http://ozlabs.org/~anton/junkcode/dscr_inherit_test.c Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Haren Myneni <haren@us.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/powerpc/kernel/sysfs.c4
-rw-r--r--arch/powerpc/kernel/traps.c3
2 files changed, 5 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index d62af950695b..cd51a5c71376 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -194,8 +194,10 @@ static ssize_t show_dscr_default(struct sysdev_class *class,
static void update_dscr(void *dummy)
{
- if (!current->thread.dscr_inherit)
+ if (!current->thread.dscr_inherit) {
+ current->thread.dscr = dscr_default;
mtspr(SPRN_DSCR, dscr_default);
+ }
}
static ssize_t __used store_dscr_default(struct sysdev_class *class,
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 1a0141426cda..6889f2676a97 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -935,8 +935,9 @@ static int emulate_instruction(struct pt_regs *regs)
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mtdscr, regs);
rd = (instword >> 21) & 0x1f;
- mtspr(SPRN_DSCR, regs->gpr[rd]);
+ current->thread.dscr = regs->gpr[rd];
current->thread.dscr_inherit = 1;
+ mtspr(SPRN_DSCR, current->thread.dscr);
return 0;
}
#endif