[PATCH v2 20/35] powerpc: add support for PREEMPT_AUTO

Ankur Arora
2024-05-28T00:36:48Z

From: Shrikanth Hegde <sshegde@linux.ibm.com>

Add PowerPC arch support for PREEMPT_AUTO by defining LAZY bits.

Since PowerPC doesn't use generic exit to functions, Add
NR_LAZY check in exit to user and exit to kernel from interrupt
routines.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
[ Changed TIF_NEED_RESCHED_LAZY to now be defined unconditionally. ]
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/thread_info.h | 5 ++++-
arch/powerpc/kernel/interrupt.c | 5 +++--
3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1c4be3373686..11e7008f5dd3 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -268,6 +268,7 @@ config PPC
select HAVE_PERF_EVENTS_NMI if PPC64
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_PREEMPT_AUTO
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE
select HAVE_RSEQ
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 15c5691dd218..0d170e2be2b6 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -117,11 +117,14 @@ void arch_setup_new_exec(void);
#endif
#define TIF_POLLING_NRFLAG 19 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_32BIT 20 /* 32 bit binary */
+#define TIF_NEED_RESCHED_LAZY 21 /* Lazy rescheduling */

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
+#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
+
#define _TIF_NOTIFY_SIGNAL (1<<TIF_NOTIFY_SIGNAL)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_32BIT (1<<TIF_32BIT)
@@ -144,7 +147,7 @@ void arch_setup_new_exec(void);
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
_TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_RESTORE_TM | _TIF_PATCH_PENDING | \
- _TIF_NOTIFY_SIGNAL)
+ _TIF_NOTIFY_SIGNAL | _TIF_NEED_RESCHED_LAZY)
#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)

/* Bits in local_flags */
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index eca293794a1e..0b97cdd4b94e 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -185,7 +185,7 @@ interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
ti_flags = read_thread_flags();
while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
local_irq_enable();
- if (ti_flags & _TIF_NEED_RESCHED) {
+ if (ti_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
schedule();
} else {
/*
@@ -396,7 +396,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
/* Returning to a kernel context with local irqs enabled. */
WARN_ON_ONCE(!(regs->msr & MSR_EE));
again:
- if (IS_ENABLED(CONFIG_PREEMPT)) {
+
+ if (IS_ENABLED(CONFIG_PREEMPTION)) {
/* Return to preemptible kernel context */
if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
if (preempt_count() == 0)
--
2.31.1