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authorLinus Torvalds <torvalds@linux-foundation.org>2022-12-12 09:01:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-12-12 09:01:36 -0800
commit98d0052d0d9dcd5323833482712b5799ed0bbb0b (patch)
treee055e679d2aebf8b11d82b010775d96794295106 /kernel/rcu
parent73fa58dca80293320f5cfeb06f5b2daeb8d97bd5 (diff)
parent6b2b0d839acaa84f05a77184370f793752e786e9 (diff)
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Merge tag 'printk-for-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek: - Add NMI-safe SRCU reader API. It uses atomic_inc() instead of this_cpu_inc() on strong load-store architectures. - Introduce new console_list_lock to synchronize a manipulation of the list of registered consoles and their flags. This is a first step in removing the big-kernel-lock-like behavior of console_lock(). This semaphore still serializes console->write() calbacks against: - each other. It primary prevents potential races between early and proper console drivers using the same device. - suspend()/resume() callbacks and init() operations in some drivers. - various other operations in the tty/vt and framebufer susbsystems. It is likely that console_lock() serializes even operations that are not directly conflicting with the console->write() callbacks here. This is the most complicated big-kernel-lock aspect of the console_lock() that will be hard to untangle. - Introduce new console_srcu lock that is used to safely iterate and access the registered console drivers under SRCU read lock. This is a prerequisite for introducing atomic console drivers and console kthreads. It will reduce the complexity of serialization against normal consoles and console_lock(). Also it should remove the risk of deadlock during critical situations, like Oops or panic, when only atomic consoles are registered. - Check whether the console is registered instead of enabled on many locations. It was a historical leftover. - Cleanly force a preferred console in xenfb code instead of a dirty hack. - A lot of code and comment clean ups and improvements. * tag 'printk-for-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (47 commits) printk: htmldocs: add missing description tty: serial: sh-sci: use setup() callback for early console printk: relieve console_lock of list synchronization duties tty: serial: kgdboc: use console_list_lock to trap exit tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() tty: serial: kgdboc: use console_list_lock for list traversal tty: serial: kgdboc: use srcu console list iterator proc: consoles: use console_list_lock for list iteration tty: tty_io: use console_list_lock for list synchronization printk, xen: fbfront: create/use safe function for forcing preferred netconsole: avoid CON_ENABLED misuse to track registration usb: early: xhci-dbc: use console_is_registered() tty: serial: xilinx_uartps: use console_is_registered() tty: serial: samsung_tty: use console_is_registered() tty: serial: pic32_uart: use console_is_registered() tty: serial: earlycon: use console_is_registered() tty: hvc: use console_is_registered() efi: earlycon: use console_is_registered() tty: nfcon: use console_is_registered() serial_core: replace uart_console_enabled() with uart_console_registered() ...
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/Kconfig11
-rw-r--r--kernel/rcu/Kconfig.debug3
-rw-r--r--kernel/rcu/rcu.h8
-rw-r--r--kernel/rcu/srcutiny.c10
-rw-r--r--kernel/rcu/update.c18
5 files changed, 26 insertions, 24 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 05106e6fbd0e..ab62074174c3 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -54,21 +54,17 @@ config RCU_EXPERT
Say N if you are unsure.
config SRCU
- bool
- help
- This option selects the sleepable version of RCU. This version
- permits arbitrary sleeping or blocking within RCU read-side critical
- sections.
+ def_bool y
config TINY_SRCU
bool
- default y if SRCU && TINY_RCU
+ default y if TINY_RCU
help
This option selects the single-CPU non-preemptible version of SRCU.
config TREE_SRCU
bool
- default y if SRCU && !TINY_RCU
+ default y if !TINY_RCU
help
This option selects the full-fledged version of SRCU.
@@ -77,7 +73,6 @@ config NEED_SRCU_NMI_SAFE
config TASKS_RCU_GENERIC
def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU
- select SRCU
help
This option enables generic infrastructure code supporting
task-based RCU implementations. Not for manual selection.
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 1b0c41d490f0..232e29fe3e5e 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -27,7 +27,6 @@ config RCU_SCALE_TEST
tristate "performance tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs performance
@@ -43,7 +42,6 @@ config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs torture tests
@@ -59,7 +57,6 @@ config RCU_REF_SCALE_TEST
tristate "Scalability tests for read-side synchronization (RCU and others)"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs performance tests
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 65704cbc9df7..c5aa934de59b 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -286,7 +286,7 @@ void rcu_test_sync_prims(void);
*/
extern void resched_cpu(int cpu);
-#if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU)
+#if !defined(CONFIG_TINY_RCU)
#include <linux/rcu_node_tree.h>
@@ -375,6 +375,10 @@ extern void rcu_init_geometry(void);
(cpu) <= rnp->grphi; \
(cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
+#endif /* !defined(CONFIG_TINY_RCU) */
+
+#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
+
/*
* Wrappers for the rcu_node::lock acquire and release.
*
@@ -437,7 +441,7 @@ do { \
#define raw_lockdep_assert_held_rcu_node(p) \
lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
-#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */
+#endif // #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 33adafdad261..b12fb0cec44d 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -197,6 +197,16 @@ void synchronize_srcu(struct srcu_struct *ssp)
{
struct rcu_synchronize rs;
+ RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
+ lock_is_held(&rcu_bh_lock_map) ||
+ lock_is_held(&rcu_lock_map) ||
+ lock_is_held(&rcu_sched_lock_map),
+ "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section");
+
+ if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
+ return;
+
+ might_sleep();
init_rcu_head_on_stack(&rs.head);
init_completion(&rs.completion);
call_srcu(ssp, &rs.head, wakeme_after_rcu);
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 738842c4886b..f5e6a2f95a2a 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -224,7 +224,7 @@ void rcu_test_sync_prims(void)
synchronize_rcu_expedited();
}
-#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
+#if !defined(CONFIG_TINY_RCU)
/*
* Switch to run-time mode once RCU has fully initialized.
@@ -239,7 +239,7 @@ static int __init rcu_set_runtime_mode(void)
}
core_initcall(rcu_set_runtime_mode);
-#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
+#endif /* #if !defined(CONFIG_TINY_RCU) */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
@@ -559,10 +559,8 @@ static void early_boot_test_call_rcu(void)
struct early_boot_kfree_rcu *rhp;
call_rcu(&head, test_callback);
- if (IS_ENABLED(CONFIG_SRCU)) {
- early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
- call_srcu(&early_srcu, &shead, test_callback);
- }
+ early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
+ call_srcu(&early_srcu, &shead, test_callback);
rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
if (!WARN_ON_ONCE(!rhp))
kfree_rcu(rhp, rh);
@@ -585,11 +583,9 @@ static int rcu_verify_early_boot_tests(void)
if (rcu_self_test) {
early_boot_test_counter++;
rcu_barrier();
- if (IS_ENABLED(CONFIG_SRCU)) {
- early_boot_test_counter++;
- srcu_barrier(&early_srcu);
- WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
- }
+ early_boot_test_counter++;
+ srcu_barrier(&early_srcu);
+ WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
}
if (rcu_self_test_counter != early_boot_test_counter) {
WARN_ON(1);