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, 60 insertions, 0 deletions

diff --git a/Documentation/driver-api/hw-recoverable-errors.rst b/Documentation/driver-api/hw-recoverable-errors.rst
new file mode 100644
index 000000000..fc526c345
--- /dev/null
+++ b/Documentation/driver-api/hw-recoverable-errors.rst
@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================================
+Recoverable Hardware Error Tracking in vmcoreinfo
+=================================================
+
+Overview
+--------
+
+This feature provides a generic infrastructure within the Linux kernel to track
+and log recoverable hardware errors. These are hardware recoverable errors
+visible that might not cause immediate panics but may influence health, mainly
+because new code path will be executed in the kernel.
+
+By recording counts and timestamps of recoverable errors into the vmcoreinfo
+crash dump notes, this infrastructure aids post-mortem crash analysis tools in
+correlating hardware events with kernel failures. This enables faster triage
+and better understanding of root causes, especially in large-scale cloud
+environments where hardware issues are common.
+
+Benefits
+--------
+
+- Facilitates correlation of hardware recoverable errors with kernel panics or
+  unusual code paths that lead to system crashes.
+- Provides operators and cloud providers quick insights, improving reliability
+  and reducing troubleshooting time.
+- Complements existing full hardware diagnostics without replacing them.
+
+Data Exposure and Consumption
+-----------------------------
+
+- The tracked error data consists of per-error-type counts and timestamps of
+  last occurrence.
+- This data is stored in the `hwerror_data` array, categorized by error source
+  types like CPU, memory, PCI, CXL, and others.
+- It is exposed via vmcoreinfo crash dump notes and can be read using tools
+  like `crash`, `drgn`, or other kernel crash analysis utilities.
+- There is no other way to read these data other than from crash dumps.
+- These errors are divided by area, which includes CPU, Memory, PCI, CXL and
+  others.
+
+Typical usage example (in drgn REPL):
+
+.. code-block:: python
+
+    >>> prog['hwerror_data']
+    (struct hwerror_info[HWERR_RECOV_MAX]){
+        {
+            .count = (int)844,
+            .timestamp = (time64_t)1752852018,
+        },
+        ...
+    }
+
+Enabling
+--------
+
+- This feature is enabled when CONFIG_VMCORE_INFO is set.
+