diff options
Diffstat (limited to 'debian/patches-rt/0002-signal-Don-t-disable-preemption-in-ptrace_stop-on-PR.patch')
| -rw-r--r-- | debian/patches-rt/0002-signal-Don-t-disable-preemption-in-ptrace_stop-on-PR.patch | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/debian/patches-rt/0002-signal-Don-t-disable-preemption-in-ptrace_stop-on-PR.patch b/debian/patches-rt/0002-signal-Don-t-disable-preemption-in-ptrace_stop-on-PR.patch new file mode 100644 index 0000000000..01e89d97ab --- /dev/null +++ b/debian/patches-rt/0002-signal-Don-t-disable-preemption-in-ptrace_stop-on-PR.patch @@ -0,0 +1,48 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 3 Aug 2023 12:09:32 +0200 +Subject: [PATCH 2/2] signal: Don't disable preemption in ptrace_stop() on + PREEMPT_RT. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +On PREEMPT_RT keeping preemption disabled during the invocation of +cgroup_enter_frozen() is a problem because the function acquires css_set_lock +which is a sleeping lock on PREEMPT_RT and must not be acquired with disabled +preemption. +The preempt-disabled section is only for performance optimisation +reasons and can be avoided. + +Extend the comment and don't disable preemption before scheduling on +PREEMPT_RT. + +Acked-by: Oleg Nesterov <oleg@redhat.com> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Link: https://lore.kernel.org/r/20230803100932.325870-3-bigeasy@linutronix.de +--- + kernel/signal.c | 13 +++++++++++-- + 1 file changed, 11 insertions(+), 2 deletions(-) + +--- a/kernel/signal.c ++++ b/kernel/signal.c +@@ -2344,11 +2344,20 @@ static int ptrace_stop(int exit_code, in + * The preempt-disable section ensures that there will be no preemption + * between unlock and schedule() and so improving the performance since + * the ptracer has no reason to sleep. ++ * ++ * On PREEMPT_RT locking tasklist_lock does not disable preemption. ++ * Therefore the task can be preempted (after ++ * do_notify_parent_cldstop()) before unlocking tasklist_lock so there ++ * is no benefit in doing this. The optimisation is harmful on ++ * PEEMPT_RT because the spinlock_t (in cgroup_enter_frozen()) must not ++ * be acquired with disabled preemption. + */ +- preempt_disable(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_disable(); + read_unlock(&tasklist_lock); + cgroup_enter_frozen(); +- preempt_enable_no_resched(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_enable_no_resched(); + schedule(); + cgroup_leave_frozen(true); + |