[GIT PULL] make Jump Labels work early

From: Jeremy Fitzhardinge
Date: Tue Nov 01 2011 - 20:32:35 EST

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Hi all,

This is the series which makes jump labels work early. Does someone want to pick this up, or
should I just send it to Linus directly?

[ I see Linus has already picked up the stop-machine patch from -mm. ]

Thanks,
J

The following changes since commit a102a9ece5489e1718cd7543aa079082450ac3a2:

Linux 3.1-rc8 (2011-09-27 15:48:34 -0700)

are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git upstream/jump-label-noearly

Jeremy Fitzhardinge (9):
jump_label: use proper atomic_t initializer
stop_machine: make stop_machine safe and efficient to call early
jump_label: if a key has already been initialized, don't nop it out
x86/jump_label: drop arch_jump_label_text_poke_early()
sparc/jump_label: drop arch_jump_label_text_poke_early()
jump_label: add arch_jump_label_transform_static() to optimise non-live code updates
s390/jump-label: add arch_jump_label_transform_static()
x86/jump_label: add arch_jump_label_transform_static()
jump-label: initialize jump-label subsystem much earlier

arch/s390/kernel/jump_label.c | 51 ++++++++++++++++++++++++---------------
arch/sparc/kernel/jump_label.c | 8 ------
arch/x86/kernel/jump_label.c | 20 +++++++++++----
include/linux/jump_label.h | 23 +++++++++++-------
init/main.c | 3 ++
kernel/jump_label.c | 37 ++++++++++++++++------------
kernel/stop_machine.c | 22 +++++++++++++++++
7 files changed, 105 insertions(+), 59 deletions(-)

diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
index 44cc06b..b987ab2 100644
--- a/arch/s390/kernel/jump_label.c
+++ b/arch/s390/kernel/jump_label.c
@@ -18,26 +18,15 @@ struct insn {
} __packed;

struct insn_args {
- unsigned long *target;
- struct insn *insn;
- ssize_t size;
+ struct jump_entry *entry;
+ enum jump_label_type type;
};

-static int __arch_jump_label_transform(void *data)
+static void __jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type)
{
- struct insn_args *args = data;
- int rc;
-
- rc = probe_kernel_write(args->target, args->insn, args->size);
- WARN_ON_ONCE(rc < 0);
- return 0;
-}
-
-void arch_jump_label_transform(struct jump_entry *entry,
- enum jump_label_type type)
-{
- struct insn_args args;
struct insn insn;
+ int rc;

if (type == JUMP_LABEL_ENABLE) {
/* brcl 15,offset */
@@ -49,11 +38,33 @@ void arch_jump_label_transform(struct jump_entry *entry,
insn.offset = 0;
}

- args.target = (void *) entry->code;
- args.insn = &insn;
- args.size = JUMP_LABEL_NOP_SIZE;
+ rc = probe_kernel_write((void *)entry->code, &insn, JUMP_LABEL_NOP_SIZE);
+ WARN_ON_ONCE(rc < 0);
+}

- stop_machine(__arch_jump_label_transform, &args, NULL);
+static int __sm_arch_jump_label_transform(void *data)
+{
+ struct insn_args *args = data;
+
+ __jump_label_transform(args->entry, args->type);
+ return 0;
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ struct insn_args args;
+
+ args.entry = entry;
+ args.type = type;
+
+ stop_machine(__sm_arch_jump_label_transform, &args, NULL);
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ __jump_label_transform(entry, type);
}

#endif
diff --git a/arch/sparc/kernel/jump_label.c b/arch/sparc/kernel/jump_label.c
index ea2dafc..971fd43 100644
--- a/arch/sparc/kernel/jump_label.c
+++ b/arch/sparc/kernel/jump_label.c
@@ -36,12 +36,4 @@ void arch_jump_label_transform(struct jump_entry *entry,
put_online_cpus();
}

-void arch_jump_label_text_poke_early(jump_label_t addr)
-{
- u32 *insn_p = (u32 *) (unsigned long) addr;
-
- *insn_p = 0x01000000;
- flushi(insn_p);
-}
-
#endif
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 3fee346..ea9d5f2f 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -24,8 +24,9 @@ union jump_code_union {
} __attribute__((packed));
};

-void arch_jump_label_transform(struct jump_entry *entry,
- enum jump_label_type type)
+static void __jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type,
+ void *(*poker)(void *, const void *, size_t))
{
union jump_code_union code;

@@ -35,17 +36,24 @@ void arch_jump_label_transform(struct jump_entry *entry,
(entry->code + JUMP_LABEL_NOP_SIZE);
} else
memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
+
+ (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type)
+{
get_online_cpus();
mutex_lock(&text_mutex);
- text_poke_smp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+ __jump_label_transform(entry, type, text_poke_smp);
mutex_unlock(&text_mutex);
put_online_cpus();
}

-void arch_jump_label_text_poke_early(jump_label_t addr)
+void arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
{
- text_poke_early((void *)addr, ideal_nops[NOP_ATOMIC5],
- JUMP_LABEL_NOP_SIZE);
+ __jump_label_transform(entry, type, text_poke_early);
}

#endif
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 66f23dc..388b0d4 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -16,7 +16,7 @@ struct jump_label_key {

# include <asm/jump_label.h>
# define HAVE_JUMP_LABEL
-#endif
+#endif /* CC_HAVE_ASM_GOTO && CONFIG_JUMP_LABEL */

enum jump_label_type {
JUMP_LABEL_DISABLE = 0,
@@ -28,9 +28,9 @@ struct module;
#ifdef HAVE_JUMP_LABEL

#ifdef CONFIG_MODULES
-#define JUMP_LABEL_INIT {{ 0 }, NULL, NULL}
+#define JUMP_LABEL_INIT {ATOMIC_INIT(0), NULL, NULL}
#else
-#define JUMP_LABEL_INIT {{ 0 }, NULL}
+#define JUMP_LABEL_INIT {ATOMIC_INIT(0), NULL}
#endif

static __always_inline bool static_branch(struct jump_label_key *key)
@@ -41,18 +41,20 @@ static __always_inline bool static_branch(struct jump_label_key *key)
extern struct jump_entry __start___jump_table[];
extern struct jump_entry __stop___jump_table[];

+extern void jump_label_init(void);
extern void jump_label_lock(void);
extern void jump_label_unlock(void);
extern void arch_jump_label_transform(struct jump_entry *entry,
- enum jump_label_type type);
-extern void arch_jump_label_text_poke_early(jump_label_t addr);
+ enum jump_label_type type);
+extern void arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type);
extern int jump_label_text_reserved(void *start, void *end);
extern void jump_label_inc(struct jump_label_key *key);
extern void jump_label_dec(struct jump_label_key *key);
extern bool jump_label_enabled(struct jump_label_key *key);
extern void jump_label_apply_nops(struct module *mod);

-#else
+#else /* !HAVE_JUMP_LABEL */

#include <linux/atomic.h>

@@ -62,6 +64,10 @@ struct jump_label_key {
atomic_t enabled;
};

+static __always_inline void jump_label_init(void)
+{
+}
+
static __always_inline bool static_branch(struct jump_label_key *key)
{
if (unlikely(atomic_read(&key->enabled)))
@@ -96,7 +102,6 @@ static inline int jump_label_apply_nops(struct module *mod)
{
return 0;
}
+#endif /* HAVE_JUMP_LABEL */

-#endif
-
-#endif
+#endif /* _LINUX_JUMP_LABEL_H */
diff --git a/init/main.c b/init/main.c
index 2a9b88a..29d8d84 100644
--- a/init/main.c
+++ b/init/main.c
@@ -515,6 +515,9 @@ asmlinkage void __init start_kernel(void)
parse_args("Booting kernel", static_command_line, __start___param,
__stop___param - __start___param,
&unknown_bootoption);
+
+ jump_label_init();
+
/*
* These use large bootmem allocations and must precede
* kmem_cache_init()
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index a8ce450..bbdfe2a 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -104,6 +104,18 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
return 0;
}

+/*
+ * Update code which is definitely not currently executing.
+ * Architectures which need heavyweight synchronization to modify
+ * running code can override this to make the non-live update case
+ * cheaper.
+ */
+void __weak arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ arch_jump_label_transform(entry, type);
+}
+
static void __jump_label_update(struct jump_label_key *key,
struct jump_entry *entry,
struct jump_entry *stop, int enable)
@@ -121,14 +133,7 @@ static void __jump_label_update(struct jump_label_key *key,
}
}

-/*
- * Not all archs need this.
- */
-void __weak arch_jump_label_text_poke_early(jump_label_t addr)
-{
-}
-
-static __init int jump_label_init(void)
+void __init jump_label_init(void)
{
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __stop___jump_table;
@@ -139,22 +144,22 @@ static __init int jump_label_init(void)
jump_label_sort_entries(iter_start, iter_stop);

for (iter = iter_start; iter < iter_stop; iter++) {
- arch_jump_label_text_poke_early(iter->code);
- if (iter->key == (jump_label_t)(unsigned long)key)
+ struct jump_label_key *iterk;
+
+ iterk = (struct jump_label_key *)(unsigned long)iter->key;
+ arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
+ JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
+ if (iterk == key)
continue;

- key = (struct jump_label_key *)(unsigned long)iter->key;
- atomic_set(&key->enabled, 0);
+ key = iterk;
key->entries = iter;
#ifdef CONFIG_MODULES
key->next = NULL;
#endif
}
jump_label_unlock();
-
- return 0;
}
-early_initcall(jump_label_init);

#ifdef CONFIG_MODULES

@@ -212,7 +217,7 @@ void jump_label_apply_nops(struct module *mod)
return;

for (iter = iter_start; iter < iter_stop; iter++)
- arch_jump_label_text_poke_early(iter->code);
+ arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
}

static int jump_label_add_module(struct module *mod)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index ba5070c..d3f960a 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -41,6 +41,7 @@ struct cpu_stopper {
};

static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
+static bool stop_machine_initialized = false;

static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
{
@@ -386,6 +387,8 @@ static int __init cpu_stop_init(void)
cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu);
register_cpu_notifier(&cpu_stop_cpu_notifier);

+ stop_machine_initialized = true;
+
return 0;
}
early_initcall(cpu_stop_init);
@@ -485,6 +488,25 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
.num_threads = num_online_cpus(),
.active_cpus = cpus };

+ if (!stop_machine_initialized) {
+ /*
+ * Handle the case where stop_machine() is called
+ * early in boot before stop_machine() has been
+ * initialized.
+ */
+ unsigned long flags;
+ int ret;
+
+ WARN_ON_ONCE(smdata.num_threads != 1);
+
+ local_irq_save(flags);
+ hard_irq_disable();
+ ret = (*fn)(data);
+ local_irq_restore(flags);
+
+ return ret;
+ }
+
/* Set the initial state and stop all online cpus. */
set_state(&smdata, STOPMACHINE_PREPARE);
return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata);

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Next message: Jeremy Fitzhardinge: "Re: [GIT PULL] Xen time-setting"
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