Merge branch 'rework/atomic-flush-hardlockup' into for-linus (475bb520) · Commits · git / linux-nf

kernel/printk/nbcon.c

+44 −5

Original line number	Diff line number	Diff line
		@@ -118,6 +118,9 @@
		* from scratch.
		*/

		/* Counter of active nbcon emergency contexts. */
		static atomic_t nbcon_cpu_emergency_cnt = ATOMIC_INIT(0);

		/**
		* nbcon_state_set - Helper function to set the console state
		* @con: Console to update
		@@ -1163,6 +1166,17 @@ static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_contex
		if (kthread_should_stop())
		return true;

		/*
		* Block the kthread when the system is in an emergency or panic mode.
		* It increases the chance that these contexts would be able to show
		* the messages directly. And it reduces the risk of interrupted writes
		* where the context with a higher priority takes over the nbcon console
		* ownership in the middle of a message.
		*/
		if (unlikely(atomic_read(&nbcon_cpu_emergency_cnt)) \|\|
		unlikely(panic_in_progress()))
		return false;

		cookie = console_srcu_read_lock();

		flags = console_srcu_read_flags(con);
		@@ -1214,6 +1228,14 @@ static int nbcon_kthread_func(void *__console)
		if (kthread_should_stop())
		return 0;

		/*
		* Block the kthread when the system is in an emergency or panic
		* mode. See nbcon_kthread_should_wakeup() for more details.
		*/
		if (unlikely(atomic_read(&nbcon_cpu_emergency_cnt)) \|\|
		unlikely(panic_in_progress()))
		goto wait_for_event;

		backlog = false;

		/*
		@@ -1505,10 +1527,10 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
		ctxt->prio = nbcon_get_default_prio();
		ctxt->allow_unsafe_takeover = allow_unsafe_takeover;

		while (nbcon_seq_read(con) < stop_seq) {
		if (!nbcon_context_try_acquire(ctxt, false))
		return -EPERM;

		while (nbcon_seq_read(con) < stop_seq) {
		/*
		* nbcon_emit_next_record() returns false when the console was
		* handed over or taken over. In both cases the context is no
		@@ -1517,6 +1539,8 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
		if (!nbcon_emit_next_record(&wctxt, true))
		return -EAGAIN;

		nbcon_context_release(ctxt);

		if (!ctxt->backlog) {
		/* Are there reserved but not yet finalized records? */
		if (nbcon_seq_read(con) < stop_seq)
		@@ -1525,7 +1549,6 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
		}
		}

		nbcon_context_release(ctxt);
		return err;
		}

		@@ -1655,6 +1678,8 @@ void nbcon_cpu_emergency_enter(void)

		preempt_disable();

		atomic_inc(&nbcon_cpu_emergency_cnt);

		cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting();
		(*cpu_emergency_nesting)++;
		}
		@@ -1669,10 +1694,24 @@ void nbcon_cpu_emergency_exit(void)
		unsigned int *cpu_emergency_nesting;

		cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting();

		if (!WARN_ON_ONCE(*cpu_emergency_nesting == 0))
		(*cpu_emergency_nesting)--;

		/*
		* Wake up kthreads because there might be some pending messages
		* added by other CPUs with normal priority since the last flush
		* in the emergency context.
		*/
		if (!WARN_ON_ONCE(atomic_read(&nbcon_cpu_emergency_cnt) == 0)) {
		if (atomic_dec_return(&nbcon_cpu_emergency_cnt) == 0) {
		struct console_flush_type ft;

		printk_get_console_flush_type(&ft);
		if (ft.nbcon_offload)
		nbcon_kthreads_wake();
		}
		}

		preempt_enable();
		}