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authorLinus Torvalds <torvalds@linux-foundation.org>2021-06-29 12:07:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-29 12:07:18 -0700
commite563592c3e4296780e5a184a917b8b86e126f0b3 (patch)
tree3f52a0f2976dd29505f05a94b1ff80b9c6c8f517 /kernel/printk
parentb694011a4aec3e8df98bc59fdb78e018b09de79d (diff)
parent94f2be50badfa88e96033e77621c6711d58f84d3 (diff)
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Merge tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek: - Add %pt[RT]s modifier to vsprintf(). It overrides ISO 8601 separator by using ' ' (space). It produces "YYYY-mm-dd HH:MM:SS" instead of "YYYY-mm-ddTHH:MM:SS". - Correctly parse long row of numbers by sscanf() when using the field width. Add extensive sscanf() selftest. - Generalize re-entrant CPU lock that has already been used to serialize dump_stack() output. It is part of the ongoing printk rework. It will allow to remove the obsoleted printk_safe buffers and introduce atomic consoles. - Some code clean up and sparse warning fixes. * tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: fix cpu lock ordering lib/dump_stack: move cpu lock to printk.c printk: Remove trailing semicolon in macros random32: Fix implicit truncation warning in prandom_seed_state() lib: test_scanf: Remove pointless use of type_min() with unsigned types selftests: lib: Add wrapper script for test_scanf lib: test_scanf: Add tests for sscanf number conversion lib: vsprintf: Fix handling of number field widths in vsscanf lib: vsprintf: scanf: Negative number must have field width > 1 usb: host: xhci-tegra: Switch to use %ptTs nilfs2: Switch to use %ptTs kdb: Switch to use %ptTs lib/vsprintf: Allow to override ISO 8601 date and time separator
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c116
1 files changed, 116 insertions, 0 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 421c35571797..142a58d124d9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3531,3 +3531,119 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
#endif
+
+#ifdef CONFIG_SMP
+static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1);
+static atomic_t printk_cpulock_nested = ATOMIC_INIT(0);
+
+/**
+ * __printk_wait_on_cpu_lock() - Busy wait until the printk cpu-reentrant
+ * spinning lock is not owned by any CPU.
+ *
+ * Context: Any context.
+ */
+void __printk_wait_on_cpu_lock(void)
+{
+ do {
+ cpu_relax();
+ } while (atomic_read(&printk_cpulock_owner) != -1);
+}
+EXPORT_SYMBOL(__printk_wait_on_cpu_lock);
+
+/**
+ * __printk_cpu_trylock() - Try to acquire the printk cpu-reentrant
+ * spinning lock.
+ *
+ * If no processor has the lock, the calling processor takes the lock and
+ * becomes the owner. If the calling processor is already the owner of the
+ * lock, this function succeeds immediately.
+ *
+ * Context: Any context. Expects interrupts to be disabled.
+ * Return: 1 on success, otherwise 0.
+ */
+int __printk_cpu_trylock(void)
+{
+ int cpu;
+ int old;
+
+ cpu = smp_processor_id();
+
+ /*
+ * Guarantee loads and stores from this CPU when it is the lock owner
+ * are _not_ visible to the previous lock owner. This pairs with
+ * __printk_cpu_unlock:B.
+ *
+ * Memory barrier involvement:
+ *
+ * If __printk_cpu_trylock:A reads from __printk_cpu_unlock:B, then
+ * __printk_cpu_unlock:A can never read from __printk_cpu_trylock:B.
+ *
+ * Relies on:
+ *
+ * RELEASE from __printk_cpu_unlock:A to __printk_cpu_unlock:B
+ * of the previous CPU
+ * matching
+ * ACQUIRE from __printk_cpu_trylock:A to __printk_cpu_trylock:B
+ * of this CPU
+ */
+ old = atomic_cmpxchg_acquire(&printk_cpulock_owner, -1,
+ cpu); /* LMM(__printk_cpu_trylock:A) */
+ if (old == -1) {
+ /*
+ * This CPU is now the owner and begins loading/storing
+ * data: LMM(__printk_cpu_trylock:B)
+ */
+ return 1;
+
+ } else if (old == cpu) {
+ /* This CPU is already the owner. */
+ atomic_inc(&printk_cpulock_nested);
+ return 1;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(__printk_cpu_trylock);
+
+/**
+ * __printk_cpu_unlock() - Release the printk cpu-reentrant spinning lock.
+ *
+ * The calling processor must be the owner of the lock.
+ *
+ * Context: Any context. Expects interrupts to be disabled.
+ */
+void __printk_cpu_unlock(void)
+{
+ if (atomic_read(&printk_cpulock_nested)) {
+ atomic_dec(&printk_cpulock_nested);
+ return;
+ }
+
+ /*
+ * This CPU is finished loading/storing data:
+ * LMM(__printk_cpu_unlock:A)
+ */
+
+ /*
+ * Guarantee loads and stores from this CPU when it was the
+ * lock owner are visible to the next lock owner. This pairs
+ * with __printk_cpu_trylock:A.
+ *
+ * Memory barrier involvement:
+ *
+ * If __printk_cpu_trylock:A reads from __printk_cpu_unlock:B,
+ * then __printk_cpu_trylock:B reads from __printk_cpu_unlock:A.
+ *
+ * Relies on:
+ *
+ * RELEASE from __printk_cpu_unlock:A to __printk_cpu_unlock:B
+ * of this CPU
+ * matching
+ * ACQUIRE from __printk_cpu_trylock:A to __printk_cpu_trylock:B
+ * of the next CPU
+ */
+ atomic_set_release(&printk_cpulock_owner,
+ -1); /* LMM(__printk_cpu_unlock:B) */
+}
+EXPORT_SYMBOL(__printk_cpu_unlock);
+#endif /* CONFIG_SMP */