Merge tag 'io_uring-7.3-20261002' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linuxgrafted

Pull io_uring fixes from Jens Axboe:

 - Fix a task_work add use-after-free with SQPOLL.

   The sqpoll thread could pop and complete the last request while
   io_req_normal_work_add() was still looking at them after the mpscq
   push.

   Use the same approach as DEFER_TASKRUN to protect from that, holding
   an RCU read lock across the add, and have exit wait for an RCU grace
   period for SQPOLL rings as well.

 - CQE32 ring fixes: correct the free entry check for 32b CQEs, zero the
   big_cqe for aux CQEs, and only post the dummy skip CQE on CQE_MIXED
   rings

 - Mark the source filter table as COW when cloning bpf filters, so
   registering another filter on the source doesn't modify the shared
   table in place

 - Initialize the task context before running the BPF loop

 - Requeue zcrx multishot receives stopped by a local resource

 - End a TX_TIMESTAMP multishot cmd when the CQ is full (lollipopkit)

* tag 'io_uring-7.3-20261002' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux:
  io_uring: fix task_work add use-after-free with SQPOLL
  io_uring/cmd_net: end TX_TIMESTAMP multishot when the CQ is full
  io_uring/zcrx: requeue multishot receives stopped by a local resource
  io_uring: initialize task context before running the BPF loop
  io_uring: zero big_cqe for aux CQEs on CQE32 rings
  io_uring: fix free entry check for 32b CQEs on CQE32 rings
  io_uring: only post the dummy skip CQE on CQE_MIXED rings
  io_uring/bpf_filter: mark source as COW when cloning filters

1 files changed, 195 insertions, 0 deletions

diff --git a/tools/lib/python/jobserver.py b/tools/lib/python/jobserver.py
new file mode 100755
index 000000000..0b1ffdf9f
--- /dev/null
+++ b/tools/lib/python/jobserver.py
@@ -0,0 +1,195 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0+
+#
+# pylint: disable=C0103,C0209
+#
+#
+
+"""
+Interacts with the POSIX jobserver during the Kernel build time.
+
+A "normal" jobserver task, like the one initiated by a make subprocess would do:
+
+    - open read/write file descriptors to communicate with the job server;
+    - ask for one slot by calling::
+
+        claim = os.read(reader, 1)
+
+    - when the job finishes, call::
+
+        os.write(writer, b"+")  # os.write(writer, claim)
+
+Here, the goal is different: This script aims to get the remaining number
+of slots available, using all of them to run a command which handle tasks in
+parallel. To to that, it has a loop that ends only after there are no
+slots left. It then increments the number by one, in order to allow a
+call equivalent to ``make -j$((claim+1))``, e.g. having a parent make creating
+$claim child to do the actual work.
+
+The end goal here is to keep the total number of build tasks under the
+limit established by the initial ``make -j$n_proc`` call.
+
+See:
+    https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
+"""
+
+import errno
+import os
+import subprocess
+import sys
+
+def warn(text, *args):
+    print(f'WARNING: {text}', *args, file = sys.stderr)
+
+class JobserverExec:
+    """
+    Claim all slots from make using POSIX Jobserver.
+
+    The main methods here are:
+
+    - open(): reserves all slots;
+    - close(): method returns all used slots back to make;
+    - run(): executes a command setting PARALLELISM=<available slots jobs + 1>.
+    """
+
+    def __init__(self):
+        """Initialize internal vars."""
+        self.claim = 0
+        self.jobs = b""
+        self.reader = None
+        self.writer = None
+        self.is_open = False
+
+    def open(self):
+        """Reserve all available slots to be claimed later on."""
+
+        if self.is_open:
+            return
+        self.is_open = True  # We only try once
+        self.claim = None
+        #
+        # Check the make flags for "--jobserver=R,W"
+        # Note that GNU Make has used --jobserver-fds and --jobserver-auth
+        # so this handles all of them.
+        #
+        flags = os.environ.get('MAKEFLAGS', '')
+        opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
+        if not opts:
+            return
+        #
+        # Separate out the provided file descriptors
+        #
+        split_opt = opts[-1].split('=', 1)
+        if len(split_opt) != 2:
+            warn('unparseable option:', opts[-1])
+            return
+        fds = split_opt[1]
+        #
+        # As of GNU Make 4.4, we'll be looking for a named pipe
+        # identified as fifo:path
+        #
+        if fds.startswith('fifo:'):
+            path = fds[len('fifo:'):]
+            try:
+                self.reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
+                self.writer = os.open(path, os.O_WRONLY)
+            except (OSError, IOError):
+                warn('unable to open jobserver pipe', path)
+                return
+        #
+        # Otherwise look for integer file-descriptor numbers.
+        #
+        else:
+            split_fds = fds.split(',')
+            if len(split_fds) != 2:
+                warn('malformed jobserver file descriptors:', fds)
+                return
+            try:
+                self.reader = int(split_fds[0])
+                self.writer = int(split_fds[1])
+            except ValueError:
+                warn('non-integer jobserver file-descriptors:', fds)
+                return
+            try:
+                #
+                # Open a private copy of reader to avoid setting nonblocking
+                # on an unexpecting process with the same reader fd.
+                #
+                self.reader = os.open(f"/proc/self/fd/{self.reader}",
+                                      os.O_RDONLY | os.O_NONBLOCK)
+            except (IOError, OSError) as e:
+                warn('Unable to reopen jobserver read-side pipe:', repr(e))
+                return
+        #
+        # OK, we have the channel to the job server; read out as many jobserver
+        # slots as possible.
+        #
+        while True:
+            try:
+                slot = os.read(self.reader, 8)
+                if not slot:
+                    #
+                    # Something went wrong.  Clear self.jobs to avoid writing
+                    # weirdness back to the jobserver and give up.
+                    self.jobs = b""
+                    warn("unexpected empty token from jobserver;"
+                         " possible invalid '--jobserver-auth=' setting")
+                    self.claim = None
+                    return
+            except (OSError, IOError) as e:
+                #
+                # If there is nothing more to read then we are done.
+                #
+                if e.errno == errno.EWOULDBLOCK:
+                    break
+                #
+                # Anything else says that something went weird; give back
+                # the jobs and give up.
+                #
+                if self.jobs:
+                    os.write(self.writer, self.jobs)
+                    self.claim = None
+                    warn('error reading from jobserver pipe', repr(e))
+                    return
+            self.jobs += slot
+        #
+        # Add a bump for our caller's reserveration, since we're just going
+        # to sit here blocked on our child.
+        #
+        self.claim = len(self.jobs) + 1
+
+    def close(self):
+        """Return all reserved slots to Jobserver."""
+
+        if not self.is_open:
+            return
+
+        # Return all the reserved slots.
+        if len(self.jobs):
+            os.write(self.writer, self.jobs)
+
+        self.is_open = False
+
+    def __enter__(self):
+        self.open()
+        return self
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        self.close()
+
+    def run(self, cmd, *args, **pwargs):
+        """
+        Run a command setting PARALLELISM env variable to the number of
+        available job slots (claim) + 1, e.g. it will reserve claim slots
+        to do the actual build work, plus one to monitor its children.
+        """
+        self.open()             # Ensure that self.claim is set
+
+        # We can only claim parallelism if there was a jobserver (i.e. a
+        # top-level "-jN" argument) and there were no other failures. Otherwise
+        # leave out the environment variable and let the child figure out what
+        # is best.
+        if self.claim:
+            os.environ["PARALLELISM"] = str(self.claim)
+
+        return subprocess.call(cmd, *args, **pwargs)