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authorChangbin Du <changbin.du@intel.com>2017-11-30 11:39:43 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-12-20 10:07:15 +0100
commitd760f903419509d933b27d387854eb1e35f88cdf (patch)
tree96db620d8d710c8077b8049e12a2bfceff141c95 /kernel
parentd1175423ce67bd1903c4f876ba6774e3a48abdc1 (diff)
tracing: Allocate mask_str buffer dynamically
commit 90e406f96f630c07d631a021fd4af10aac913e77 upstream. The default NR_CPUS can be very large, but actual possible nr_cpu_ids usually is very small. For my x86 distribution, the NR_CPUS is 8192 and nr_cpu_ids is 4. About 2 pages are wasted. Most machines don't have so many CPUs, so define a array with NR_CPUS just wastes memory. So let's allocate the buffer dynamically when need. With this change, the mutext tracing_cpumask_update_lock also can be removed now, which was used to protect mask_str. Link: http://lkml.kernel.org/r/1512013183-19107-1-git-send-email-changbin.du@intel.com Fixes: 36dfe9252bd4c ("ftrace: make use of tracing_cpumask") Signed-off-by: Changbin Du <changbin.du@intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c29
1 files changed, 9 insertions, 20 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c1e50cc0d7b0..4214cd960b8e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3727,37 +3727,30 @@ static const struct file_operations show_traces_fops = {
.llseek = seq_lseek,
};
-/*
- * The tracer itself will not take this lock, but still we want
- * to provide a consistent cpumask to user-space:
- */
-static DEFINE_MUTEX(tracing_cpumask_update_lock);
-
-/*
- * Temporary storage for the character representation of the
- * CPU bitmask (and one more byte for the newline):
- */
-static char mask_str[NR_CPUS + 1];
-
static ssize_t
tracing_cpumask_read(struct file *filp, char __user *ubuf,
size_t count, loff_t *ppos)
{
struct trace_array *tr = file_inode(filp)->i_private;
+ char *mask_str;
int len;
- mutex_lock(&tracing_cpumask_update_lock);
+ len = snprintf(NULL, 0, "%*pb\n",
+ cpumask_pr_args(tr->tracing_cpumask)) + 1;
+ mask_str = kmalloc(len, GFP_KERNEL);
+ if (!mask_str)
+ return -ENOMEM;
- len = snprintf(mask_str, count, "%*pb\n",
+ len = snprintf(mask_str, len, "%*pb\n",
cpumask_pr_args(tr->tracing_cpumask));
if (len >= count) {
count = -EINVAL;
goto out_err;
}
- count = simple_read_from_buffer(ubuf, count, ppos, mask_str, NR_CPUS+1);
+ count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len);
out_err:
- mutex_unlock(&tracing_cpumask_update_lock);
+ kfree(mask_str);
return count;
}
@@ -3777,8 +3770,6 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
if (err)
goto err_unlock;
- mutex_lock(&tracing_cpumask_update_lock);
-
local_irq_disable();
arch_spin_lock(&tr->max_lock);
for_each_tracing_cpu(cpu) {
@@ -3801,8 +3792,6 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
local_irq_enable();
cpumask_copy(tr->tracing_cpumask, tracing_cpumask_new);
-
- mutex_unlock(&tracing_cpumask_update_lock);
free_cpumask_var(tracing_cpumask_new);
return count;