Commit 00619f7c authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched,livepatch: Use task_call_func() 



Instead of frobbing around with scheduler internals, use the shiny new
task_call_func() interface.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Tested-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.709906138@infradead.org
parent 9b3c4ab3

kernel/livepatch/transition.c

+44 −46
Original line number Diff line number Diff line
@@ -13,7 +13,6 @@ 
#include "core.h"

#include "patch.h"

#include "transition.h"

#include "../sched/sched.h"



#define MAX_STACK_ENTRIES  100

#define STACK_ERR_BUF_SIZE 128
@@ -240,7 +239,7 @@ static int klp_check_stack_func(struct klp_func *func, unsigned long *entries, 
 * Determine whether it's safe to transition the task to the target patch state

 * by looking for any to-be-patched or to-be-unpatched functions on its stack.

 */

static int klp_check_stack(struct task_struct *task, char *err_buf)

static int klp_check_stack(struct task_struct *task, const char **oldname)

{

	static unsigned long entries[MAX_STACK_ENTRIES];

	struct klp_object *obj;
@@ -248,12 +247,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) 
	int ret, nr_entries;



	ret = stack_trace_save_tsk_reliable(task, entries, ARRAY_SIZE(entries));

	if (ret < 0) {

		snprintf(err_buf, STACK_ERR_BUF_SIZE,

			 "%s: %s:%d has an unreliable stack\n",

			 __func__, task->comm, task->pid);

		return ret;

	}

	if (ret < 0)

		return -EINVAL;

	nr_entries = ret;



	klp_for_each_object(klp_transition_patch, obj) {
@@ -262,11 +257,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) 
		klp_for_each_func(obj, func) {

			ret = klp_check_stack_func(func, entries, nr_entries);

			if (ret) {

				snprintf(err_buf, STACK_ERR_BUF_SIZE,

					 "%s: %s:%d is sleeping on function %s\n",

					 __func__, task->comm, task->pid,

					 func->old_name);

				return ret;

				*oldname = func->old_name;

				return -EADDRINUSE;

			}

		}

	}
@@ -274,6 +266,22 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) 
	return 0;

}



static int klp_check_and_switch_task(struct task_struct *task, void *arg)

{

	int ret;



	if (task_curr(task) && task != current)

		return -EBUSY;



	ret = klp_check_stack(task, arg);

	if (ret)

		return ret;



	clear_tsk_thread_flag(task, TIF_PATCH_PENDING);

	task->patch_state = klp_target_state;

	return 0;

}



/*

 * Try to safely switch a task to the target patch state.  If it's currently

 * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or
@@ -281,13 +289,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) 
 */

static bool klp_try_switch_task(struct task_struct *task)

{

	static char err_buf[STACK_ERR_BUF_SIZE];

	struct rq *rq;

	struct rq_flags flags;

	const char *old_name;

	int ret;

	bool success = false;



	err_buf[0] = '\0';



	/* check if this task has already switched over */

	if (task->patch_state == klp_target_state)
@@ -305,36 +308,31 @@ static bool klp_try_switch_task(struct task_struct *task) 
	 * functions.  If all goes well, switch the task to the target patch

	 * state.

	 */

	rq = task_rq_lock(task, &flags);



	if (task_running(rq, task) && task != current) {

		snprintf(err_buf, STACK_ERR_BUF_SIZE,

			 "%s: %s:%d is running\n", __func__, task->comm,

			 task->pid);

		goto done;

	}

	ret = task_call_func(task, klp_check_and_switch_task, &old_name);

	switch (ret) {

	case 0:		/* success */

		break;



	ret = klp_check_stack(task, err_buf);

	if (ret)

		goto done;



	success = true;



	clear_tsk_thread_flag(task, TIF_PATCH_PENDING);

	task->patch_state = klp_target_state;



done:

	task_rq_unlock(rq, task, &flags);

	case -EBUSY:	/* klp_check_and_switch_task() */

		pr_debug("%s: %s:%d is running\n",

			 __func__, task->comm, task->pid);

		break;

	case -EINVAL:	/* klp_check_and_switch_task() */

		pr_debug("%s: %s:%d has an unreliable stack\n",

			 __func__, task->comm, task->pid);

		break;

	case -EADDRINUSE: /* klp_check_and_switch_task() */

		pr_debug("%s: %s:%d is sleeping on function %s\n",

			 __func__, task->comm, task->pid, old_name);

		break;



	/*

	 * Due to console deadlock issues, pr_debug() can't be used while

	 * holding the task rq lock.  Instead we have to use a temporary buffer

	 * and print the debug message after releasing the lock.

	 */

	if (err_buf[0] != '\0')

		pr_debug("%s", err_buf);

	default:

		pr_debug("%s: Unknown error code (%d) when trying to switch %s:%d\n",

			 __func__, ret, task->comm, task->pid);

		break;

	}



	return success;

	return !ret;

}



/*