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Message-ID: <20081027163046.GA20692@Krystal>
Date: Mon, 27 Oct 2008 12:30:46 -0400
From: Mathieu Desnoyers <compudj@...stal.dyndns.org>
To: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Ingo Molnar <mingo@...e.hu>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH tip/tracing/markers] new probes manager
* Mathieu Desnoyers (mathieu.desnoyers@...ymtl.ca) wrote:
> * Lai Jiangshan (laijs@...fujitsu.com) wrote:
> >
> > this patch use a new probes manager for marker.
> >
> > the most important benefit of this patch is:
> > 1) smp_rmb() is removed from the critical path. as we know rmb()
> > is very expensive.
> >
>
> Do you have performance measurements for this ? On x86 it's a nop,
> AFAIK.
My statement above is inexact : x86_64 uses lfence for rmb(). But
numbers would still be welcome.
MAthieu
>
> > the other benefits:
> > 2) Now, unused memory is handled by struct marker_probes.
> >
> > old code use these three field to handle unused memory.
> > struct marker_entry {
> > ...
> > struct rcu_head rcu;
> > void *oldptr;
> > int rcu_pending;
> > ...
> > };
> > in this way, unused memory is handled by struct marker_entry.
> > it bring reenter bug(it was fixed) and marker.c is filled
> > full of ".*rcu.*" code statements. this patch remove all these.
> >
>
> Hrm, I think this will utterly slow down the batch
> registration/unregistration. Can you try to register 100 markers in
> batch on a loaded machine (e.g. running tbench on all cores) and see
> how long it takes ? Comparing before/after your patch would be welcome.
>
> I have merged the modules_mutex, tracepoint_mutex and marker_mutex in
> the -lttng tree. It makes locking much much simpler and actually fixes
> an issue we currently have with interrupt unregister marker by private
> data (the entry is not there anymore when we do the second get within
> the unregister).
>
> Can you have a look at these changes ?
>
> > 3) use new probes manager, and remove the "single optimization",
> > and remove hundreds of codes. "single optimization" indeed
> > speedup register/unregister side, but it brings smp_rmb()
> > in the critical path, and brings a lots of code.
> >
>
> Nope. Single probe optimization makes sure we don't dynamically allocate
> memory for a single probe, it's not there for register/unregister speed
> at all. It also makes sure we don't reference another cache-line
> uselessly when we have a single probe.
>
> Performance impact of this change should be better tested/caracterized.
>
> > and the size of struct marker is reduced. struct marker's
> > memory is pre-allocated by compiler. this fix will save
> > this memory.
>
> This is mostly cache-cold stuff. And the thing we really care about is
> the amount of cache-lines used when the marker is active with a single
> probe. Your change seems to degrade this.
>
> >
> > about struct marker.state and immediate value:
> > 4) struct marker.state is removed, for it equals to
> > struct marker.multi != NULL
> > and struct marker.multi can use immediate value also in future.
> >
>
> Given the single vs multi probes are better vs cache-line usage, I still
> see the need for marker.state, which is a single char which fits in the
> same cache-line as marker.ptype.
>
> Mathieu
>
> >
> > Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> > ---
> > include/linux/marker.h | 12 -
> > kernel/marker.c | 552 +++++++++++++------------------------------------
> > 2 files changed, 150 insertions(+), 414 deletions(-)
> > diff --git a/include/linux/marker.h b/include/linux/marker.h
> > index 4aca94a..179c59a 100644
> > --- a/include/linux/marker.h
> > +++ b/include/linux/marker.h
> > @@ -43,11 +43,8 @@ struct marker {
> > const char *format; /* Marker format string, describing the
> > * variable argument list.
> > */
> > - char state; /* Marker state. */
> > - char ptype; /* probe type : 0 : single, 1 : multi */
> > - /* Probe wrapper */
> > +
> > void (*call)(const struct marker *mdata, void *call_private, ...);
> > - struct marker_probe_closure single;
> > struct marker_probe_closure *multi;
> > } __attribute__((aligned(8)));
> >
> > @@ -72,10 +69,9 @@ struct marker {
> > static struct marker __mark_##name \
> > __attribute__((section("__markers"), aligned(8))) = \
> > { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)], \
> > - 0, 0, marker_probe_cb, \
> > - { __mark_empty_function, NULL}, NULL }; \
> > + marker_probe_cb, NULL }; \
> > __mark_check_format(format, ## args); \
> > - if (unlikely(__mark_##name.state)) { \
> > + if (unlikely(__mark_##name.multi)) { \
> > (*__mark_##name.call) \
> > (&__mark_##name, call_private, ## args);\
> > } \
> > @@ -133,8 +129,6 @@ static inline void __printf(1, 2) ___mark_check_format(const char *fmt, ...)
> > ___mark_check_format(format, ## args); \
> > } while (0)
> >
> > -extern marker_probe_func __mark_empty_function;
> > -
> > extern void marker_probe_cb(const struct marker *mdata,
> > void *call_private, ...);
> >
> > diff --git a/kernel/marker.c b/kernel/marker.c
> > index 2898b64..dee5bd3 100644
> > --- a/kernel/marker.c
> > +++ b/kernel/marker.c
> > @@ -1,5 +1,6 @@
> > /*
> > * Copyright (C) 2007 Mathieu Desnoyers
> > + * Copyright (C) 2008 Lai Jiangshan
> > *
> > * This program is free software; you can redistribute it and/or modify
> > * it under the terms of the GNU General Public License as published by
> > @@ -55,89 +56,32 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
> > */
> > struct marker_entry {
> > struct hlist_node hlist;
> > - char *format;
> > + const char *format;
> > /* Probe wrapper */
> > void (*call)(const struct marker *mdata, void *call_private, ...);
> > - struct marker_probe_closure single;
> > struct marker_probe_closure *multi;
> > - int refcount; /* Number of times armed. 0 if disarmed. */
> > - struct rcu_head rcu;
> > - void *oldptr;
> > - int rcu_pending;
> > - unsigned char ptype:1;
> > + int refcount; /* Number of probes */
> > unsigned char format_allocated:1;
> > - char name[0]; /* Contains name'\0'format'\0' */
> > + const char name[0]; /* Contains name'\0'format'\0' */
> > };
> >
> > /**
> > - * __mark_empty_function - Empty probe callback
> > - * @probe_private: probe private data
> > - * @call_private: call site private data
> > - * @fmt: format string
> > - * @...: variable argument list
> > - *
> > - * Empty callback provided as a probe to the markers. By providing this to a
> > - * disabled marker, we make sure the execution flow is always valid even
> > - * though the function pointer change and the marker enabling are two distinct
> > - * operations that modifies the execution flow of preemptible code.
> > - */
> > -void __mark_empty_function(void *probe_private, void *call_private,
> > - const char *fmt, va_list *args)
> > -{
> > -}
> > -EXPORT_SYMBOL_GPL(__mark_empty_function);
> > -
> > -/*
> > - * marker_probe_cb Callback that prepares the variable argument list for probes.
> > + * marker_probe_cb - Call probes with the variable argument list
> > * @mdata: pointer of type struct marker
> > * @call_private: caller site private data
> > * @...: Variable argument list.
> > - *
> > - * Since we do not use "typical" pointer based RCU in the 1 argument case, we
> > - * need to put a full smp_rmb() in this branch. This is why we do not use
> > - * rcu_dereference() for the pointer read.
> > */
> > void marker_probe_cb(const struct marker *mdata, void *call_private, ...)
> > {
> > va_list args;
> > - char ptype;
> > + struct marker_probe_closure *multi;
> >
> > - /*
> > - * rcu_read_lock_sched does two things : disabling preemption to make
> > - * sure the teardown of the callbacks can be done correctly when they
> > - * are in modules and they insure RCU read coherency.
> > - */
> > rcu_read_lock_sched();
> > - ptype = mdata->ptype;
> > - if (likely(!ptype)) {
> > - marker_probe_func *func;
> > - /* Must read the ptype before ptr. They are not data dependant,
> > - * so we put an explicit smp_rmb() here. */
> > - smp_rmb();
> > - func = mdata->single.func;
> > - /* Must read the ptr before private data. They are not data
> > - * dependant, so we put an explicit smp_rmb() here. */
> > - smp_rmb();
> > - va_start(args, call_private);
> > - func(mdata->single.probe_private, call_private, mdata->format,
> > - &args);
> > - va_end(args);
> > - } else {
> > - struct marker_probe_closure *multi;
> > + /* reload mdata->multi again with rcu_read_lock_sched() held. */
> > + multi = rcu_dereference(mdata->multi);
> > + /* recheck multi after reload */
> > + if (multi) {
> > int i;
> > - /*
> > - * Read mdata->ptype before mdata->multi.
> > - */
> > - smp_rmb();
> > - multi = mdata->multi;
> > - /*
> > - * multi points to an array, therefore accessing the array
> > - * depends on reading multi. However, even in this case,
> > - * we must insure that the pointer is read _before_ the array
> > - * data. Same as rcu_dereference, but we need a full smp_rmb()
> > - * in the fast path, so put the explicit barrier here.
> > - */
> > - smp_read_barrier_depends();
> > for (i = 0; multi[i].func; i++) {
> > va_start(args, call_private);
> > multi[i].func(multi[i].probe_private, call_private,
> > @@ -149,48 +93,26 @@ void marker_probe_cb(const struct marker *mdata, void *call_private, ...)
> > }
> > EXPORT_SYMBOL_GPL(marker_probe_cb);
> >
> > -/*
> > - * marker_probe_cb Callback that does not prepare the variable argument list.
> > +/**
> > + * marker_probe_cb_noarg - Call probes without variable argument list
> > * @mdata: pointer of type struct marker
> > * @call_private: caller site private data
> > * @...: Variable argument list.
> > *
> > * Should be connected to markers "MARK_NOARGS".
> > */
> > -static void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
> > +static void marker_probe_cb_noarg(const struct marker *mdata,
> > + void *call_private, ...)
> > {
> > - va_list args; /* not initialized */
> > - char ptype;
> > + va_list args;
> > + struct marker_probe_closure *multi;
> >
> > rcu_read_lock_sched();
> > - ptype = mdata->ptype;
> > - if (likely(!ptype)) {
> > - marker_probe_func *func;
> > - /* Must read the ptype before ptr. They are not data dependant,
> > - * so we put an explicit smp_rmb() here. */
> > - smp_rmb();
> > - func = mdata->single.func;
> > - /* Must read the ptr before private data. They are not data
> > - * dependant, so we put an explicit smp_rmb() here. */
> > - smp_rmb();
> > - func(mdata->single.probe_private, call_private, mdata->format,
> > - &args);
> > - } else {
> > - struct marker_probe_closure *multi;
> > + /* reload mdata->multi again with rcu_read_lock_sched() held. */
> > + multi = rcu_dereference(mdata->multi);
> > + /* recheck multi after reload */
> > + if (multi) {
> > int i;
> > - /*
> > - * Read mdata->ptype before mdata->multi.
> > - */
> > - smp_rmb();
> > - multi = mdata->multi;
> > - /*
> > - * multi points to an array, therefore accessing the array
> > - * depends on reading multi. However, even in this case,
> > - * we must insure that the pointer is read _before_ the array
> > - * data. Same as rcu_dereference, but we need a full smp_rmb()
> > - * in the fast path, so put the explicit barrier here.
> > - */
> > - smp_read_barrier_depends();
> > for (i = 0; multi[i].func; i++)
> > multi[i].func(multi[i].probe_private, call_private,
> > mdata->format, &args);
> > @@ -198,14 +120,35 @@ static void marker_probe_cb_noarg(const struct marker *mdata, void *call_private
> > rcu_read_unlock_sched();
> > }
> >
> > -static void free_old_closure(struct rcu_head *head)
> > +struct marker_probes {
> > + struct rcu_head rcu;
> > + struct marker_probe_closure multi[0];
> > +};
> > +
> > +static inline struct marker_probe_closure *allocate_probe_closure(int count)
> > +{
> > + struct marker_probes *p;
> > + p = kmalloc(count * sizeof(struct marker_probe_closure)
> > + + sizeof(struct marker_probes), GFP_KERNEL);
> > + if (!p)
> > + return NULL;
> > + return p->multi;
> > +}
> > +
> > +static void rcu_free_old_closure(struct rcu_head *head)
> > {
> > - struct marker_entry *entry = container_of(head,
> > - struct marker_entry, rcu);
> > - kfree(entry->oldptr);
> > - /* Make sure we free the data before setting the pending flag to 0 */
> > - smp_wmb();
> > - entry->rcu_pending = 0;
> > + struct marker_probes *probes = container_of(head,
> > + struct marker_probes, rcu);
> > + kfree(probes);
> > +}
> > +
> > +static inline void release_probe_closure(struct marker_probe_closure *old)
> > +{
> > + if (old) {
> > + struct marker_probes *probes = container_of(old,
> > + struct marker_probes, multi[0]);
> > + call_rcu(&probes->rcu, rcu_free_old_closure);
> > + }
> > }
> >
> > static void debug_print_probes(struct marker_entry *entry)
> > @@ -215,69 +158,40 @@ static void debug_print_probes(struct marker_entry *entry)
> > if (!marker_debug)
> > return;
> >
> > - if (!entry->ptype) {
> > - printk(KERN_DEBUG "Single probe : %p %p\n",
> > - entry->single.func,
> > - entry->single.probe_private);
> > - } else {
> > - for (i = 0; entry->multi[i].func; i++)
> > - printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
> > - entry->multi[i].func,
> > - entry->multi[i].probe_private);
> > - }
> > + for (i = 0; i < entry->refcount; i++)
> > + printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
> > + entry->multi[i].func,
> > + entry->multi[i].probe_private);
> > }
> >
> > static struct marker_probe_closure *
> > marker_entry_add_probe(struct marker_entry *entry,
> > marker_probe_func *probe, void *probe_private)
> > {
> > - int nr_probes = 0;
> > + int nr_probes = entry->refcount, i;
> > struct marker_probe_closure *old, *new;
> >
> > - WARN_ON(!probe);
> > + if (!probe)
> > + return ERR_PTR(-EINVAL);
> >
> > debug_print_probes(entry);
> > old = entry->multi;
> > - if (!entry->ptype) {
> > - if (entry->single.func == probe &&
> > - entry->single.probe_private == probe_private)
> > + for (i = 0; i < nr_probes; i++)
> > + if (old[i].func == probe
> > + && old[i].probe_private == probe_private)
> > return ERR_PTR(-EBUSY);
> > - if (entry->single.func == __mark_empty_function) {
> > - /* 0 -> 1 probes */
> > - entry->single.func = probe;
> > - entry->single.probe_private = probe_private;
> > - entry->refcount = 1;
> > - entry->ptype = 0;
> > - debug_print_probes(entry);
> > - return NULL;
> > - } else {
> > - /* 1 -> 2 probes */
> > - nr_probes = 1;
> > - old = NULL;
> > - }
> > - } else {
> > - /* (N -> N+1), (N != 0, 1) probes */
> > - for (nr_probes = 0; old[nr_probes].func; nr_probes++)
> > - if (old[nr_probes].func == probe
> > - && old[nr_probes].probe_private
> > - == probe_private)
> > - return ERR_PTR(-EBUSY);
> > - }
> > +
> > /* + 2 : one for new probe, one for NULL func */
> > - new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
> > - GFP_KERNEL);
> > - if (new == NULL)
> > + new = allocate_probe_closure(nr_probes + 2);
> > + if (!new)
> > return ERR_PTR(-ENOMEM);
> > - if (!old)
> > - new[0] = entry->single;
> > - else
> > - memcpy(new, old,
> > - nr_probes * sizeof(struct marker_probe_closure));
> > + memcpy(new, old, nr_probes * sizeof(struct marker_probe_closure));
> > new[nr_probes].func = probe;
> > new[nr_probes].probe_private = probe_private;
> > + new[nr_probes + 1].func = NULL;
> > + new[nr_probes + 1].probe_private = NULL;
> > entry->refcount = nr_probes + 1;
> > entry->multi = new;
> > - entry->ptype = 1;
> > debug_print_probes(entry);
> > return old;
> > }
> > @@ -286,60 +200,33 @@ static struct marker_probe_closure *
> > marker_entry_remove_probe(struct marker_entry *entry,
> > marker_probe_func *probe, void *probe_private)
> > {
> > - int nr_probes = 0, nr_del = 0, i;
> > + int nr_probes = entry->refcount, nr_del = 0, i;
> > struct marker_probe_closure *old, *new;
> >
> > - old = entry->multi;
> > -
> > debug_print_probes(entry);
> > - if (!entry->ptype) {
> > - /* 0 -> N is an error */
> > - WARN_ON(entry->single.func == __mark_empty_function);
> > - /* 1 -> 0 probes */
> > - WARN_ON(probe && entry->single.func != probe);
> > - WARN_ON(entry->single.probe_private != probe_private);
> > - entry->single.func = __mark_empty_function;
> > - entry->refcount = 0;
> > - entry->ptype = 0;
> > - debug_print_probes(entry);
> > - return NULL;
> > - } else {
> > - /* (N -> M), (N > 1, M >= 0) probes */
> > - for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
> > - if ((!probe || old[nr_probes].func == probe)
> > - && old[nr_probes].probe_private
> > - == probe_private)
> > - nr_del++;
> > - }
> > + old = entry->multi;
> > + for (i = 0; i < nr_probes; i++) {
> > + if ((!probe || old[i].func == probe)
> > + && old[i].probe_private == probe_private)
> > + nr_del++;
> > }
> >
> > if (nr_probes - nr_del == 0) {
> > - /* N -> 0, (N > 1) */
> > - entry->single.func = __mark_empty_function;
> > entry->refcount = 0;
> > - entry->ptype = 0;
> > - } else if (nr_probes - nr_del == 1) {
> > - /* N -> 1, (N > 1) */
> > - for (i = 0; old[i].func; i++)
> > - if ((probe && old[i].func != probe) ||
> > - old[i].probe_private != probe_private)
> > - entry->single = old[i];
> > - entry->refcount = 1;
> > - entry->ptype = 0;
> > + entry->multi = NULL;
> > } else {
> > int j = 0;
> > - /* N -> M, (N > 1, M > 1) */
> > /* + 1 for NULL */
> > - new = kzalloc((nr_probes - nr_del + 1)
> > - * sizeof(struct marker_probe_closure), GFP_KERNEL);
> > - if (new == NULL)
> > + new = allocate_probe_closure(nr_probes - nr_del + 1);
> > + if (!new)
> > return ERR_PTR(-ENOMEM);
> > - for (i = 0; old[i].func; i++)
> > + for (i = 0; i < nr_probes; i++)
> > if ((probe && old[i].func != probe) ||
> > old[i].probe_private != probe_private)
> > new[j++] = old[i];
> > + new[nr_probes - nr_del].func = NULL;
> > + new[nr_probes - nr_del].probe_private = NULL;
> > entry->refcount = nr_probes - nr_del;
> > - entry->ptype = 1;
> > entry->multi = new;
> > }
> > debug_print_probes(entry);
> > @@ -358,7 +245,7 @@ static struct marker_entry *get_marker(const char *name)
> > struct marker_entry *e;
> > u32 hash = jhash(name, strlen(name), 0);
> >
> > - head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > + head = &marker_table[hash & (MARKER_TABLE_SIZE - 1)];
> > hlist_for_each_entry(e, node, head, hlist) {
> > if (!strcmp(name, e->name))
> > return e;
> > @@ -373,22 +260,14 @@ static struct marker_entry *get_marker(const char *name)
> > static struct marker_entry *add_marker(const char *name, const char *format)
> > {
> > struct hlist_head *head;
> > - struct hlist_node *node;
> > struct marker_entry *e;
> > size_t name_len = strlen(name) + 1;
> > size_t format_len = 0;
> > - u32 hash = jhash(name, name_len-1, 0);
> > + u32 hash = jhash(name, name_len - 1, 0);
> >
> > + head = &marker_table[hash & (MARKER_TABLE_SIZE - 1)];
> > if (format)
> > format_len = strlen(format) + 1;
> > - head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > - hlist_for_each_entry(e, node, head, hlist) {
> > - if (!strcmp(name, e->name)) {
> > - printk(KERN_NOTICE
> > - "Marker %s busy\n", name);
> > - return ERR_PTR(-EBUSY); /* Already there */
> > - }
> > - }
> > /*
> > * Using kmalloc here to allocate a variable length element. Could
> > * cause some memory fragmentation if overused.
> > @@ -397,10 +276,10 @@ static struct marker_entry *add_marker(const char *name, const char *format)
> > GFP_KERNEL);
> > if (!e)
> > return ERR_PTR(-ENOMEM);
> > - memcpy(&e->name[0], name, name_len);
> > + memcpy((void *)&e->name[0], name, name_len);
> > if (format) {
> > e->format = &e->name[name_len];
> > - memcpy(e->format, format, format_len);
> > + memcpy((void *)e->format, format, format_len);
> > if (strcmp(e->format, MARK_NOARGS) == 0)
> > e->call = marker_probe_cb_noarg;
> > else
> > @@ -411,13 +290,9 @@ static struct marker_entry *add_marker(const char *name, const char *format)
> > e->format = NULL;
> > e->call = marker_probe_cb;
> > }
> > - e->single.func = __mark_empty_function;
> > - e->single.probe_private = NULL;
> > e->multi = NULL;
> > - e->ptype = 0;
> > e->format_allocated = 0;
> > e->refcount = 0;
> > - e->rcu_pending = 0;
> > hlist_add_head(&e->hlist, head);
> > return e;
> > }
> > @@ -426,38 +301,16 @@ static struct marker_entry *add_marker(const char *name, const char *format)
> > * Remove the marker from the marker hash table. Must be called with mutex_lock
> > * held.
> > */
> > -static int remove_marker(const char *name)
> > +static inline void remove_marker(struct marker_entry *entry)
> > {
> > - struct hlist_head *head;
> > - struct hlist_node *node;
> > - struct marker_entry *e;
> > - int found = 0;
> > - size_t len = strlen(name) + 1;
> > - u32 hash = jhash(name, len-1, 0);
> > -
> > - head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > - hlist_for_each_entry(e, node, head, hlist) {
> > - if (!strcmp(name, e->name)) {
> > - found = 1;
> > - break;
> > - }
> > - }
> > - if (!found)
> > - return -ENOENT;
> > - if (e->single.func != __mark_empty_function)
> > - return -EBUSY;
> > - hlist_del(&e->hlist);
> > - if (e->format_allocated)
> > - kfree(e->format);
> > - /* Make sure the call_rcu has been executed */
> > - if (e->rcu_pending)
> > - rcu_barrier_sched();
> > - kfree(e);
> > - return 0;
> > + hlist_del(&entry->hlist);
> > + if (entry->format_allocated)
> > + kfree(entry->format);
> > + kfree(entry);
> > }
> >
> > /*
> > - * Set the mark_entry format to the format found in the element.
> > + * Set the mark_entry format to the format.
> > */
> > static int marker_set_format(struct marker_entry *entry, const char *format)
> > {
> > @@ -466,6 +319,11 @@ static int marker_set_format(struct marker_entry *entry, const char *format)
> > return -ENOMEM;
> > entry->format_allocated = 1;
> >
> > + if (strcmp(entry->format, MARK_NOARGS) == 0)
> > + entry->call = marker_probe_cb_noarg;
> > + else
> > + entry->call = marker_probe_cb;
> > +
> > trace_mark(core_marker_format, "name %s format %s",
> > entry->name, entry->format);
> > return 0;
> > @@ -474,8 +332,7 @@ static int marker_set_format(struct marker_entry *entry, const char *format)
> > /*
> > * Sets the probe callback corresponding to one marker.
> > */
> > -static int set_marker(struct marker_entry *entry, struct marker *elem,
> > - int active)
> > +static int set_marker(struct marker_entry *entry, struct marker *elem)
> > {
> > int ret;
> > WARN_ON(strcmp(entry->name, elem->name) != 0);
> > @@ -503,56 +360,18 @@ static int set_marker(struct marker_entry *entry, struct marker *elem,
> > * callback (does not set arguments).
> > */
> > elem->call = entry->call;
> > - /*
> > - * Sanity check :
> > - * We only update the single probe private data when the ptr is
> > - * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
> > - */
> > - WARN_ON(elem->single.func != __mark_empty_function
> > - && elem->single.probe_private != entry->single.probe_private
> > - && !elem->ptype);
> > - elem->single.probe_private = entry->single.probe_private;
> > - /*
> > - * Make sure the private data is valid when we update the
> > - * single probe ptr.
> > - */
> > - smp_wmb();
> > - elem->single.func = entry->single.func;
> > - /*
> > - * We also make sure that the new probe callbacks array is consistent
> > - * before setting a pointer to it.
> > - */
> > +
> > rcu_assign_pointer(elem->multi, entry->multi);
> > - /*
> > - * Update the function or multi probe array pointer before setting the
> > - * ptype.
> > - */
> > - smp_wmb();
> > - elem->ptype = entry->ptype;
> > - elem->state = active;
> >
> > return 0;
> > }
> >
> > /*
> > * Disable a marker and its probe callback.
> > - * Note: only waiting an RCU period after setting elem->call to the empty
> > - * function insures that the original callback is not used anymore. This insured
> > - * by rcu_read_lock_sched around the call site.
> > */
> > -static void disable_marker(struct marker *elem)
> > +static inline void disable_marker(struct marker *elem)
> > {
> > - /* leave "call" as is. It is known statically. */
> > - elem->state = 0;
> > - elem->single.func = __mark_empty_function;
> > - /* Update the function before setting the ptype */
> > - smp_wmb();
> > - elem->ptype = 0; /* single probe */
> > - /*
> > - * Leave the private data and id there, because removal is racy and
> > - * should be done only after an RCU period. These are never used until
> > - * the next initialization anyway.
> > - */
> > + rcu_assign_pointer(elem->multi, NULL);
> > }
> >
> > /**
> > @@ -562,8 +381,7 @@ static void disable_marker(struct marker *elem)
> > *
> > * Updates the probe callback corresponding to a range of markers.
> > */
> > -void marker_update_probe_range(struct marker *begin,
> > - struct marker *end)
> > +void marker_update_probe_range(struct marker *begin, struct marker *end)
> > {
> > struct marker *iter;
> > struct marker_entry *mark_entry;
> > @@ -572,7 +390,7 @@ void marker_update_probe_range(struct marker *begin,
> > for (iter = begin; iter < end; iter++) {
> > mark_entry = get_marker(iter->name);
> > if (mark_entry) {
> > - set_marker(mark_entry, iter, !!mark_entry->refcount);
> > + set_marker(mark_entry, iter);
> > /*
> > * ignore error, continue
> > */
> > @@ -585,20 +403,6 @@ void marker_update_probe_range(struct marker *begin,
> >
> > /*
> > * Update probes, removing the faulty probes.
> > - *
> > - * Internal callback only changed before the first probe is connected to it.
> > - * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
> > - * transitions. All other transitions will leave the old private data valid.
> > - * This makes the non-atomicity of the callback/private data updates valid.
> > - *
> > - * "special case" updates :
> > - * 0 -> 1 callback
> > - * 1 -> 0 callback
> > - * 1 -> 2 callbacks
> > - * 2 -> 1 callbacks
> > - * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
> > - * Site effect : marker_set_format may delete the marker entry (creating a
> > - * replacement).
> > */
> > static void marker_update_probes(void)
> > {
> > @@ -638,35 +442,19 @@ int marker_probe_register(const char *name, const char *format,
> > else if (strcmp(entry->format, format))
> > ret = -EPERM;
> > }
> > - if (ret)
> > - goto end;
> > + if (ret) {
> > + mutex_unlock(&markers_mutex);
> > + return ret;
> > + }
> >
> > - /*
> > - * If we detect that a call_rcu is pending for this marker,
> > - * make sure it's executed now.
> > - */
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > old = marker_entry_add_probe(entry, probe, probe_private);
> > - if (IS_ERR(old)) {
> > - ret = PTR_ERR(old);
> > - goto end;
> > - }
> > mutex_unlock(&markers_mutex);
> > + if (old && IS_ERR(old))
> > + return PTR_ERR(old);
> > +
> > marker_update_probes(); /* may update entry */
> > - mutex_lock(&markers_mutex);
> > - entry = get_marker(name);
> > - WARN_ON(!entry);
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > - entry->oldptr = old;
> > - entry->rcu_pending = 1;
> > - /* write rcu_pending before calling the RCU callback */
> > - smp_wmb();
> > - call_rcu_sched(&entry->rcu, free_old_closure);
> > -end:
> > - mutex_unlock(&markers_mutex);
> > - return ret;
> > + release_probe_closure(old);
> > + return 0;
> > }
> > EXPORT_SYMBOL_GPL(marker_probe_register);
> >
> > @@ -677,43 +465,32 @@ EXPORT_SYMBOL_GPL(marker_probe_register);
> > * @probe_private: probe private data
> > *
> > * Returns the private data given to marker_probe_register, or an ERR_PTR().
> > - * We do not need to call a synchronize_sched to make sure the probes have
> > - * finished running before doing a module unload, because the module unload
> > - * itself uses stop_machine(), which insures that every preempt disabled section
> > - * have finished.
> > */
> > int marker_probe_unregister(const char *name,
> > marker_probe_func *probe, void *probe_private)
> > {
> > struct marker_entry *entry;
> > struct marker_probe_closure *old;
> > - int ret = -ENOENT;
> >
> > mutex_lock(&markers_mutex);
> > entry = get_marker(name);
> > - if (!entry)
> > - goto end;
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > + if (!entry) {
> > + mutex_unlock(&markers_mutex);
> > + return -ENOENT;
> > + }
> > +
> > old = marker_entry_remove_probe(entry, probe, probe_private);
> > + if (!entry->refcount)
> > + remove_marker(entry);
> > +
> > mutex_unlock(&markers_mutex);
> > + if (old && IS_ERR(old))
> > + return PTR_ERR(old);
> > +
> > marker_update_probes(); /* may update entry */
> > - mutex_lock(&markers_mutex);
> > - entry = get_marker(name);
> > - if (!entry)
> > - goto end;
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > - entry->oldptr = old;
> > - entry->rcu_pending = 1;
> > - /* write rcu_pending before calling the RCU callback */
> > - smp_wmb();
> > - call_rcu_sched(&entry->rcu, free_old_closure);
> > - remove_marker(name); /* Ignore busy error message */
> > - ret = 0;
> > -end:
> > - mutex_unlock(&markers_mutex);
> > - return ret;
> > + release_probe_closure(old);
> > +
> > + return 0;
> > }
> > EXPORT_SYMBOL_GPL(marker_probe_unregister);
> >
> > @@ -728,20 +505,13 @@ get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
> > for (i = 0; i < MARKER_TABLE_SIZE; i++) {
> > head = &marker_table[i];
> > hlist_for_each_entry(entry, node, head, hlist) {
> > - if (!entry->ptype) {
> > - if (entry->single.func == probe
> > - && entry->single.probe_private
> > + struct marker_probe_closure *closure;
> > + closure = entry->multi;
> > + for (i = 0; i < entry->refcount; i++) {
> > + if (closure[i].func == probe &&
> > + closure[i].probe_private
> > == probe_private)
> > return entry;
> > - } else {
> > - struct marker_probe_closure *closure;
> > - closure = entry->multi;
> > - for (i = 0; closure[i].func; i++) {
> > - if (closure[i].func == probe &&
> > - closure[i].probe_private
> > - == probe_private)
> > - return entry;
> > - }
> > }
> > }
> > }
> > @@ -756,43 +526,32 @@ get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
> > * Unregister a probe by providing the registered private data.
> > * Only removes the first marker found in hash table.
> > * Return 0 on success or error value.
> > - * We do not need to call a synchronize_sched to make sure the probes have
> > - * finished running before doing a module unload, because the module unload
> > - * itself uses stop_machine(), which insures that every preempt disabled section
> > - * have finished.
> > */
> > int marker_probe_unregister_private_data(marker_probe_func *probe,
> > void *probe_private)
> > {
> > struct marker_entry *entry;
> > - int ret = 0;
> > struct marker_probe_closure *old;
> >
> > mutex_lock(&markers_mutex);
> > entry = get_marker_from_private_data(probe, probe_private);
> > if (!entry) {
> > - ret = -ENOENT;
> > - goto end;
> > + mutex_unlock(&markers_mutex);
> > + return -ENOENT;
> > }
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > +
> > old = marker_entry_remove_probe(entry, NULL, probe_private);
> > + if (!entry->refcount)
> > + remove_marker(entry);
> > +
> > mutex_unlock(&markers_mutex);
> > + if (old && IS_ERR(old))
> > + return PTR_ERR(old);
> > +
> > marker_update_probes(); /* may update entry */
> > - mutex_lock(&markers_mutex);
> > - entry = get_marker_from_private_data(probe, probe_private);
> > - WARN_ON(!entry);
> > - if (entry->rcu_pending)
> > - rcu_barrier_sched();
> > - entry->oldptr = old;
> > - entry->rcu_pending = 1;
> > - /* write rcu_pending before calling the RCU callback */
> > - smp_wmb();
> > - call_rcu_sched(&entry->rcu, free_old_closure);
> > - remove_marker(entry->name); /* Ignore busy error message */
> > -end:
> > - mutex_unlock(&markers_mutex);
> > - return ret;
> > + release_probe_closure(old);
> > +
> > + return 0;
> > }
> > EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
> >
> > @@ -804,7 +563,6 @@ EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
> > *
> > * Returns the nth private data pointer (starting from 0) matching, or an
> > * ERR_PTR.
> > - * Returns the private data pointer, or an ERR_PTR.
> > * The private data pointer should _only_ be dereferenced if the caller is the
> > * owner of the data, or its content could vanish. This is mostly used to
> > * confirm that a caller is the owner of a registered probe.
> > @@ -812,31 +570,15 @@ EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
> > void *marker_get_private_data(const char *name, marker_probe_func *probe,
> > int num)
> > {
> > - struct hlist_head *head;
> > - struct hlist_node *node;
> > - struct marker_entry *e;
> > - size_t name_len = strlen(name) + 1;
> > - u32 hash = jhash(name, name_len-1, 0);
> > - int i;
> > -
> > - head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > - hlist_for_each_entry(e, node, head, hlist) {
> > - if (!strcmp(name, e->name)) {
> > - if (!e->ptype) {
> > - if (num == 0 && e->single.func == probe)
> > - return e->single.probe_private;
> > - } else {
> > - struct marker_probe_closure *closure;
> > - int match = 0;
> > - closure = e->multi;
> > - for (i = 0; closure[i].func; i++) {
> > - if (closure[i].func != probe)
> > - continue;
> > - if (match++ == num)
> > - return closure[i].probe_private;
> > - }
> > - }
> > - break;
> > + struct marker_entry *e = get_marker(name);
> > + if (e) {
> > + struct marker_probe_closure *closure = e->multi;
> > + int match = 0, i;
> > + for (i = 0; i < e->refcount; i++) {
> > + if (closure[i].func != probe)
> > + continue;
> > + if (match++ == num)
> > + return closure[i].probe_private;
> > }
> > }
> > return ERR_PTR(-ENOENT);
> >
> >
>
> --
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
--
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