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panic: sys_info: rewrite a fix for a compilation error (make W=1)

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Compiler was not happy about dead variable in use:

lib/sys_info.c:52:19: error: variable 'sys_info_avail' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]
   52 | static const char sys_info_avail[] = "tasks,mem,timers,locks,ftrace,all_bt,blocked_tasks";
      |                   ^~~~~~~~~~~~~~

This was fixed by adding __maybe_unused attribute that just hides the
issue and didn't actually fix the root cause.  Rewrite the fix by moving
the local variable from stack to a heap.

As a side effect this drops unneeded "synchronisation" of duplicative info
and also makes code ready for the further refactoring.

Link: https://lkml.kernel.org/r/20251030132007.3742368-5-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Feng Tang <feng.tang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andy Shevchenko
2025-10-30 12:44:20 +01:00
committed by Andrew Morton
parent d13adc6147
commit eb72c4667f
1 changed files with 16 additions and 12 deletions
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28
lib/sys_info.c
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@@ -1,5 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/array_size.h>
#include <linux/bitops.h>
#include <linux/cleanup.h>
#include <linux/console.h>
#include <linux/log2.h>
#include <linux/kernel.h>
@@ -11,10 +13,6 @@
#include <linux/sys_info.h>
/*
* When 'si_names' gets updated, please make sure the 'sys_info_avail'
* below is updated accordingly.
*/
static const char * const si_names[] = {
[ilog2(SYS_INFO_TASKS)] = "tasks",
[ilog2(SYS_INFO_MEM)] = "mem",
@@ -45,25 +43,32 @@ unsigned long sys_info_parse_param(char *str)
#ifdef CONFIG_SYSCTL
static const char sys_info_avail[] __maybe_unused = "tasks,mem,timers,locks,ftrace,all_bt,blocked_tasks";
int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
void *buffer, size_t *lenp,
loff_t *ppos)
{
char names[sizeof(sys_info_avail)];
struct ctl_table table;
unsigned long *si_bits_global;
unsigned long si_bits;
unsigned int i;
size_t maxlen;
si_bits_global = ro_table->data;
maxlen = 0;
for (i = 0; i < ARRAY_SIZE(si_names); i++)
maxlen += strlen(si_names[i]) + 1;
char *names __free(kfree) = kzalloc(maxlen, GFP_KERNEL);
if (!names)
return -ENOMEM;
if (write) {
int ret;
table = *ro_table;
table.data = names;
table.maxlen = sizeof(names);
table.maxlen = maxlen;
ret = proc_dostring(&table, write, buffer, lenp, ppos);
if (ret)
return ret;
@@ -74,16 +79,15 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
return 0;
} else {
/* for 'read' operation */
unsigned int len = 0;
char *delim = "";
int i, len = 0;
/* The access to the global value is not synchronized. */
si_bits = READ_ONCE(*si_bits_global);
names[0] = '\0';
for_each_set_bit(i, &si_bits, ARRAY_SIZE(si_names)) {
if (*si_names[i]) {
len += scnprintf(names + len, sizeof(names) - len,
len += scnprintf(names + len, maxlen - len,
"%s%s", delim, si_names[i]);
delim = ",";
}
@@ -91,7 +95,7 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
table = *ro_table;
table.data = names;
table.maxlen = sizeof(names);
table.maxlen = maxlen;
return proc_dostring(&table, write, buffer, lenp, ppos);
}
}