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kernel/smp: Make csdlock_debug= resettable

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It is currently possible to set the csdlock_debug_enabled static
branch, but not to reset it.  This is an issue when several different
entities supply kernel boot parameters and also for kernels built with
CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT=y.

Therefore, make the csdlock_debug=0 kernel boot parameter turn off
debugging.  Last one wins!

Reported-by: Jes Sorensen <Jes.Sorensen@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20230321005516.50558-4-paulmck@kernel.org
This commit is contained in:
Paul E. McKenney 2023-03-20 17:55:16 -07:00 committed by Peter Zijlstra
parent 6366d062e7
commit 203e435844
2 changed files with 15 additions and 9 deletions
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13
Documentation/admin-guide/kernel-parameters.txt
View file

@ -889,12 +889,13 @@
cs89x0_media= [HW,NET]
Format: { rj45 | aui | bnc }
csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
handling. When switched on, additional debug data is
printed to the console in case a hanging CPU is
detected, and that CPU is pinged again in order to try
to resolve the hang situation. The default value of
this option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
function call handling. When switched on,
additional debug data is printed to the console
in case a hanging CPU is detected, and that
CPU is pinged again in order to try to resolve
the hang situation. The default value of this
option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
Kconfig option.
dasd= [HW,NET]

11
kernel/smp.c
View file

@ -116,11 +116,16 @@ static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug
*/
static int __init csdlock_debug(char *str)
{
int ret;
unsigned int val = 0;
get_option(&str, &val);
if (val)
static_branch_enable(&csdlock_debug_enabled);
ret = get_option(&str, &val);
if (ret) {
if (val)
static_branch_enable(&csdlock_debug_enabled);
else
static_branch_disable(&csdlock_debug_enabled);
}
return 1;
}