Commit f51246efee2b ("MIPS: Get rid of finish_arch_switch().") moved the __restore_watch() call from finish_arch_switch() (i.e. after resume() returns) to before the resume() call in switch_to(). This results in watchpoints only being restored when a task is descheduled, preventing the watchpoints from being effective most of the time, except due to chance before the watchpoints are lazily removed.

Fix the call sequence from switch_to() through to mips_install_watch_registers() to pass the task_struct pointer of the next task, instead of using current. This allows the watchpoints for the next (non-current) task to be restored without reintroducing finish_arch_switch().

Fixes f51246efee2b ("MIPS: Get rid of finish_arch_switch().")

Signed-off-by James Hogan <[email protected]>

Cc Paul Burton <[email protected]>

Cc [email protected]

Patchwork: https://patchwork.linux-mips.org/patch/12726/

Signed-off-by Ralf Baechle <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/mips/include/asm/switch_to.h |    2 +-
 arch/mips/include/asm/watch.h     |   10 +++++-----
 arch/mips/kernel/pm.c             |    2 +-
 arch/mips/kernel/watch.c          |    5 ++---
 4 files changed, 9 insertions(+), 10 deletions(-)

arch/mips/include/asm/switch_to.h +1 -1

@@ -105,7 +105,7 @@ do {									\
 	__clear_software_ll_bit();					\
 	if (cpu_has_userlocal)						\
 		write_c0_userlocal(task_thread_info(next)->tp_value);	\
-	__restore_watch();						\
+	__restore_watch(next);						\
 	(last) = resume(prev, next, task_thread_info(next));		\
 } while (0)

arch/mips/include/asm/watch.h +5 -5

@@ -12,21 +12,21 @@
 
 #include <asm/mipsregs.h>
 
-void mips_install_watch_registers(void);
+void mips_install_watch_registers(struct task_struct *t);
 void mips_read_watch_registers(void);
 void mips_clear_watch_registers(void);
 void mips_probe_watch_registers(struct cpuinfo_mips *c);
 
 #ifdef CONFIG_HARDWARE_WATCHPOINTS
-#define __restore_watch() do {						\
+#define __restore_watch(task) do {					\
 	if (unlikely(test_bit(TIF_LOAD_WATCH,				\
-			      &current_thread_info()->flags))) {	\
-		mips_install_watch_registers();				\
+			      &task_thread_info(task)->flags))) {	\
+		mips_install_watch_registers(task);			\
 	}								\
 } while (0)
 
 #else
-#define __restore_watch() do {} while (0)
+#define __restore_watch(task) do {} while (0)
 #endif
 
 #endif /* _ASM_WATCH_H */

arch/mips/kernel/pm.c +1 -1

@@ -56,7 +56,7 @@ static void mips_cpu_restore(void)
 		write_c0_userlocal(current_thread_info()->tp_value);
 
 	/* Restore watch registers */
-	__restore_watch();
+	__restore_watch(current);
 }
 
 /**

arch/mips/kernel/watch.c +2 -3

@@ -15,10 +15,9 @@
  * Install the watch registers for the current thread.	A maximum of
  * four registers are installed although the machine may have more.
  */
-void mips_install_watch_registers(void)
+void mips_install_watch_registers(struct task_struct *t)
 {
-	struct mips3264_watch_reg_state *watches =
-		&current->thread.watch.mips3264;
+	struct mips3264_watch_reg_state *watches = &t->thread.watch.mips3264;
 	switch (current_cpu_data.watch_reg_use_cnt) {
 	default:
 		BUG();

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/mips64-r6-r2-emulation-bugfix.patch queue-4.5/mips-fix-uapi-include-in-exported-asm-siginfo.h.patch queue-4.5/mips-disable-preemption-during-prctl-pr_set_fp_mode.patch queue-4.5/mips-fix-sigreturn-via-vdso-on-micromips-kernel.patch queue-4.5/mips-fix-siginfo.h-to-use-strict-posix-types.patch queue-4.5/mips-don-t-unwind-to-user-mode-with-eva.patch queue-4.5/mips-vdso-build-with-fno-strict-aliasing.patch queue-4.5/mips-fix-watchpoint-restoration.patch queue-4.5/mips-build-micromips-vdso-for-micromips-kernels.patch queue-4.5/mips-math-emu-fix-jalr-emulation-when-rd-0.patch queue-4.5/mips-fix-msa-ld_-st_-asm-macros-to-use-ptr_addu.patch queue-4.5/mips-avoid-using-unwind_stack-with-usermode.patch queue-4.5/mips-prevent-restoration-of-msa-context-in-non-msa-kernels.patch queue-4.5/mips-use-copy_s.fmt-rather-than-copy_u.fmt.patch