[patch V3 15/32] s390/kernel: Use stop_machine_cpuslocked()

[patch V3 15/32] s390/kernel: Use stop_machine_cpuslocked()

[Thomas Gleixner]

[-- Attachment #1: s390kernel_Use_stop_machine_cpuslocked.patch --]
[-- Type: text/plain, Size: 1339 bytes --]

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

stp_work_fn() holds get_online_cpus() while invoking stop_machine().

stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use stop_machine_cpuslocked() to avoid the nested call. Convert
*_online_cpus() to the new interfaces while at it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-s390@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>

---
 arch/s390/kernel/time.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -636,10 +636,10 @@ static void stp_work_fn(struct work_stru
 		goto out_unlock;
 
 	memset(&stp_sync, 0, sizeof(stp_sync));
-	get_online_cpus();
+	cpus_read_lock();
 	atomic_set(&stp_sync.cpus, num_online_cpus() - 1);
-	stop_machine(stp_sync_clock, &stp_sync, cpu_online_mask);
-	put_online_cpus();
+	stop_machine_cpuslocked(stp_sync_clock, &stp_sync, cpu_online_mask);
+	cpus_read_unlock();
 
 	if (!check_sync_clock())
 		/*

[patch V3 28/32] s390: Prevent hotplug rwsem recursion

[Thomas Gleixner]

[-- Attachment #1: s390--Prevent-hotplug-rwsem-recursion.patch --]
[-- Type: text/plain, Size: 1598 bytes --]

The text patching functions which are invoked from jump_label and kprobes
code are protected against cpu hotplug at the call sites.

Use stop_machine_cpuslocked() to avoid recursion on the cpu hotplug
rwsem. stop_machine_cpuslocked() contains a lockdep assertion to catch any
unprotected callers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
---
 arch/s390/kernel/jump_label.c |    2 +-
 arch/s390/kernel/kprobes.c    |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/arch/s390/kernel/jump_label.c
+++ b/arch/s390/kernel/jump_label.c
@@ -93,7 +93,7 @@ void arch_jump_label_transform(struct ju
 	args.entry = entry;
 	args.type = type;
 
-	stop_machine(__sm_arch_jump_label_transform, &args, NULL);
+	stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);
 }
 
 void arch_jump_label_transform_static(struct jump_entry *entry,
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -196,7 +196,7 @@ void arch_arm_kprobe(struct kprobe *p)
 {
 	struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 
-	stop_machine(swap_instruction, &args, NULL);
+	stop_machine_cpuslocked(swap_instruction, &args, NULL);
 }
 NOKPROBE_SYMBOL(arch_arm_kprobe);
 
@@ -204,7 +204,7 @@ void arch_disarm_kprobe(struct kprobe *p
 {
 	struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 
-	stop_machine(swap_instruction, &args, NULL);
+	stop_machine_cpuslocked(swap_instruction, &args, NULL);
 }
 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 

Re: [patch V3 15/32] s390/kernel: Use stop_machine_cpuslocked()

[Heiko Carstens]

On Wed, May 24, 2017 at 10:15:26AM +0200, Thomas Gleixner wrote:
> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> 
> stp_work_fn() holds get_online_cpus() while invoking stop_machine().
> 
> stop_machine() invokes get_online_cpus() as well. This is correct, but
> prevents the conversion of the hotplug locking to a percpu rwsem.
> 
> Use stop_machine_cpuslocked() to avoid the nested call. Convert
> *_online_cpus() to the new interfaces while at it.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-s390@vger.kernel.org
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> 
> ---
>  arch/s390/kernel/time.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>

Re: [patch V3 28/32] s390: Prevent hotplug rwsem recursion

[Heiko Carstens]

On Wed, May 24, 2017 at 10:15:39AM +0200, Thomas Gleixner wrote:
> The text patching functions which are invoked from jump_label and kprobes
> code are protected against cpu hotplug at the call sites.
> 
> Use stop_machine_cpuslocked() to avoid recursion on the cpu hotplug
> rwsem. stop_machine_cpuslocked() contains a lockdep assertion to catch any
> unprotected callers.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: linux-s390@vger.kernel.org
> ---
>  arch/s390/kernel/jump_label.c |    2 +-
>  arch/s390/kernel/kprobes.c    |    4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>