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Date: Wed, 15 Oct 2008 09:44:16 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
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] markers: simplify
marker_set_format()
* Lai Jiangshan (laijs@...fujitsu.com) wrote:
>
> current marker_set_format() is complex this patch simplify it,
> and decrease the overhead of marker_update_probes().
>
Yep, I think I did put the format string after the name \0, which was
rather tricky. I agree that such change makes the code more readable at
the expense of doing 2 allocations per marker rather than one, but
readability might be a good thing here.
Thanks !
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
> diff --git a/kernel/marker.c b/kernel/marker.c
> index e49a9c5..ef43c86 100644
> --- a/kernel/marker.c
> +++ b/kernel/marker.c
> @@ -65,6 +65,7 @@ struct marker_entry {
> void *oldptr;
> int rcu_pending;
> unsigned char ptype:1;
> + unsigned char format_allocated:1;
> char name[0]; /* Contains name'\0'format'\0' */
> };
>
> @@ -415,6 +416,7 @@ static struct marker_entry *add_marker(const char *name, const char *format)
> 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);
> @@ -446,6 +448,8 @@ static int remove_marker(const char *name)
> 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();
> @@ -456,57 +460,34 @@ static int remove_marker(const char *name)
> /*
> * Set the mark_entry format to the format found in the element.
> */
> -static int marker_set_format(struct marker_entry **entry, const char *format)
> +static int marker_set_format(struct marker_entry *entry, const char *format)
> {
> - struct marker_entry *e;
> - size_t name_len = strlen((*entry)->name) + 1;
> - size_t format_len = strlen(format) + 1;
> -
> -
> - e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
> - GFP_KERNEL);
> - if (!e)
> + entry->format = kstrdup(format, GFP_KERNEL);
> + if (!entry->format)
> return -ENOMEM;
> - memcpy(&e->name[0], (*entry)->name, name_len);
> - e->format = &e->name[name_len];
> - memcpy(e->format, format, format_len);
> - if (strcmp(e->format, MARK_NOARGS) == 0)
> - e->call = marker_probe_cb_noarg;
> - else
> - e->call = marker_probe_cb;
> - e->single = (*entry)->single;
> - e->multi = (*entry)->multi;
> - e->ptype = (*entry)->ptype;
> - e->refcount = (*entry)->refcount;
> - e->rcu_pending = 0;
> - hlist_add_before(&e->hlist, &(*entry)->hlist);
> - hlist_del(&(*entry)->hlist);
> - /* Make sure the call_rcu has been executed */
> - if ((*entry)->rcu_pending)
> - rcu_barrier_sched();
> - kfree(*entry);
> - *entry = e;
> + entry->format_allocated = 1;
> +
> trace_mark(core_marker_format, "name %s format %s",
> - e->name, e->format);
> + entry->name, entry->format);
> return 0;
> }
>
> /*
> * Sets the probe callback corresponding to one marker.
> */
> -static int set_marker(struct marker_entry **entry, struct marker *elem,
> +static int set_marker(struct marker_entry *entry, struct marker *elem,
> int active)
> {
> int ret;
> - WARN_ON(strcmp((*entry)->name, elem->name) != 0);
> + WARN_ON(strcmp(entry->name, elem->name) != 0);
>
> - if ((*entry)->format) {
> - if (strcmp((*entry)->format, elem->format) != 0) {
> + if (entry->format) {
> + if (strcmp(entry->format, elem->format) != 0) {
> printk(KERN_NOTICE
> "Format mismatch for probe %s "
> "(%s), marker (%s)\n",
> - (*entry)->name,
> - (*entry)->format,
> + entry->name,
> + entry->format,
> elem->format);
> return -EPERM;
> }
> @@ -522,34 +503,33 @@ static int set_marker(struct marker_entry **entry, struct marker *elem,
> * pass from a "safe" callback (with argument) to an "unsafe"
> * callback (does not set arguments).
> */
> - elem->call = (*entry)->call;
> + 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;
> + && 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;
> + 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);
> + 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->ptype = entry->ptype;
> elem->state = active;
>
> return 0;
> @@ -593,8 +573,7 @@ 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, !!mark_entry->refcount);
> /*
> * ignore error, continue
> */
> @@ -656,7 +635,7 @@ int marker_probe_register(const char *name, const char *format,
> ret = PTR_ERR(entry);
> } else if (format) {
> if (!entry->format)
> - ret = marker_set_format(&entry, format);
> + ret = marker_set_format(entry, format);
> else if (strcmp(entry->format, format))
> ret = -EPERM;
> }
>
>
>
>
>
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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