Commit 17f89102 authored by Tomas Glozar's avatar Tomas Glozar Committed by Steven Rostedt (Google)
Browse files

tracing/osnoise: Allow arbitrarily long CPU string 

Allocate kernel memory for processing CPU string
(/sys/kernel/tracing/osnoise/cpus) also in osnoise_cpus_write to allow
the writing of a CPU string of an arbitrary length.

This replaces the 256-byte buffer, which is insufficient with the rising
number of CPUs. For example, if I wanted to measure on every even CPU
on a system with 256 CPUs, the string would be 456 characters long.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250425091839.343289-1-tglozar@redhat.com


Signed-off-by: default avatarTomas Glozar <tglozar@redhat.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent a54665ab

kernel/trace/trace_osnoise.c

+5 −4
Original line number Diff line number Diff line
@@ -2302,7 +2302,7 @@ osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count, 
 * osnoise_cpus_write - Write function for "cpus" entry

 * @filp: The active open file structure

 * @ubuf: The user buffer that contains the value to write

 * @cnt: The maximum number of bytes to write to "file"

 * @count: The maximum number of bytes to write to "file"

 * @ppos: The current position in @file

 *

 * This function provides a write implementation for the "cpus"
@@ -2320,10 +2320,11 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count, 
{

	cpumask_var_t osnoise_cpumask_new;

	int running, err;

	char buf[256];

	char *buf __free(kfree) = NULL;



	if (count >= 256)

		return -EINVAL;

	buf = kmalloc(count, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	if (copy_from_user(buf, ubuf, count))

		return -EFAULT;