reboot: refactor and comment the cpu selection code
Small improvements to the code, without changing the way it works:
- use a local variable, to avoid a small time lapse where reboot_cpu
can have an invalid value
- comment the code which is not easy to understand at a glance
- merge two identical code blocks into one
- replace pointer arithmetics with equivalent array syntax
Link: https://lkml.kernel.org/r/20201103214025.116799-4-mcroce@linux.microsoft.com
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Robin Holt <robinmholt@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 2a18b76..aa3bfd6 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -553,20 +553,24 @@ static int __init reboot_setup(char *str)
break;
case 's':
- if (isdigit(*(str+1)))
- reboot_cpu = simple_strtoul(str+1, NULL, 0);
- else if (str[1] == 'm' && str[2] == 'p' &&
- isdigit(*(str+3)))
- reboot_cpu = simple_strtoul(str+3, NULL, 0);
- else
+ /*
+ * reboot_cpu is s[mp]#### with #### being the processor
+ * to be used for rebooting. Skip 's' or 'smp' prefix.
+ */
+ str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
+
+ if (isdigit(str[0])) {
+ int cpu = simple_strtoul(str, NULL, 0);
+
+ if (cpu >= num_possible_cpus()) {
+ pr_err("Ignoring the CPU number in reboot= option. "
+ "CPU %d exceeds possible cpu number %d\n",
+ cpu, num_possible_cpus());
+ break;
+ }
+ reboot_cpu = cpu;
+ } else
*mode = REBOOT_SOFT;
- if (reboot_cpu >= num_possible_cpus()) {
- pr_err("Ignoring the CPU number in reboot= option. "
- "CPU %d exceeds possible cpu number %d\n",
- reboot_cpu, num_possible_cpus());
- reboot_cpu = 0;
- break;
- }
break;
case 'g':
