Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.

1 files changed, 83 insertions, 0 deletions

diff --git a/lib/decompress.c b/lib/decompress.c
new file mode 100644
index 000000000..778547158
--- /dev/null
+++ b/lib/decompress.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * decompress.c
+ *
+ * Detect the decompression method based on magic number
+ */
+
+#include <linux/decompress/generic.h>
+
+#include <linux/decompress/bunzip2.h>
+#include <linux/decompress/unlzma.h>
+#include <linux/decompress/unxz.h>
+#include <linux/decompress/inflate.h>
+#include <linux/decompress/unlzo.h>
+#include <linux/decompress/unlz4.h>
+#include <linux/decompress/unzstd.h>
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/printk.h>
+
+#ifndef CONFIG_DECOMPRESS_GZIP
+# define gunzip NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_BZIP2
+# define bunzip2 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZMA
+# define unlzma NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_XZ
+# define unxz NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZO
+# define unlzo NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZ4
+# define unlz4 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_ZSTD
+# define unzstd NULL
+#endif
+
+struct compress_format {
+	unsigned char magic[2];
+	const char *name;
+	decompress_fn decompressor;
+};
+
+static const struct compress_format compressed_formats[] __initconst = {
+	{ .magic = {0x1f, 0x8b}, .name = "gzip", .decompressor = gunzip },
+	{ .magic = {0x1f, 0x9e}, .name = "gzip", .decompressor = gunzip },
+	{ .magic = {0x42, 0x5a}, .name = "bzip2", .decompressor = bunzip2 },
+	{ .magic = {0x5d, 0x00}, .name = "lzma", .decompressor = unlzma },
+	{ .magic = {0xfd, 0x37}, .name = "xz", .decompressor = unxz },
+	{ .magic = {0x89, 0x4c}, .name = "lzo", .decompressor = unlzo },
+	{ .magic = {0x02, 0x21}, .name = "lz4", .decompressor = unlz4 },
+	{ .magic = {0x28, 0xb5}, .name = "zstd", .decompressor = unzstd },
+	{ /* sentinel */ }
+};
+
+decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
+				const char **name)
+{
+	const struct compress_format *cf;
+
+	if (len < 2) {
+		if (name)
+			*name = NULL;
+		return NULL;	/* Need at least this much... */
+	}
+
+	pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
+
+	for (cf = compressed_formats; cf->name; cf++)
+		if (!memcmp(inbuf, cf->magic, 2))
+			break;
+
+	if (name)
+		*name = cf->name;
+	return cf->decompressor;
+}