kernel/linux.git/include/linux/rculist.h, branch v6.6.132

rculist: Unify documentation about missing list_empty_rcu()

2021-08-06T20:41:48+00:00

We have two separate sections that talk about why list_empty_rcu() is not needed, so this commit consolidates them. Signed-off-by: Julian Wiedmann [ paulmck: The usual wordsmithing. ] Signed-off-by: Paul E. McKenney

rculist: Introduce list/hlist_for_each_entry_srcu() macros

2020-08-25T01:36:09+00:00

list/hlist_for_each_entry_rcu() provides an optional cond argument to specify the lock held in the updater side. However for SRCU read side, not providing the cond argument results into false positive as whether srcu_read_lock is held or not is not checked implicitly. Therefore, on read side the lockdep expression srcu_read_lock_held(srcu struct) can solve this issue. However, the function still fails to check the cases where srcu protected list is traversed with rcu_read_lock() instead of srcu_read_lock(). Therefore, to remove the false negative, this patch introduces two new list traversal primitives : list_for_each_entry_srcu() and hlist_for_each_entry_srcu(). Both of the functions have non-optional cond argument as it is required for both read and update side, and simply checks if the cond is true. For regular read side the lockdep expression srcu_read_lock_head() can be passed as the cond argument to list/hlist_for_each_entry_srcu(). Suggested-by: Paolo Bonzini Tested-by: Suraj Upadhyay Tested-by: Naresh Kamboju [ paulmck: Add "true" per kbuild test robot feedback. ] Signed-off-by: Madhuparna Bhowmik Signed-off-by: Paul E. McKenney

Merge tag 'locking-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-03T21:39:35+00:00

Pull locking updates from Ingo Molnar: - LKMM updates: mostly documentation changes, but also some new litmus tests for atomic ops. - KCSAN updates: the most important change is that GCC 11 now has all fixes in place to support KCSAN, so GCC support can be enabled again. Also more annotations. - futex updates: minor cleanups and simplifications - seqlock updates: merge preparatory changes/cleanups for the 'associated locks' facilities. - lockdep updates: - simplify IRQ trace event handling - add various new debug checks - simplify header dependencies, split out , decouple lockdep from other low level headers some more - fix NMI handling - misc cleanups and smaller fixes * tag 'locking-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits) kcsan: Improve IRQ state trace reporting lockdep: Refactor IRQ trace events fields into struct seqlock: lockdep assert non-preemptibility on seqcount_t write lockdep: Add preemption enabled/disabled assertion APIs seqlock: Implement raw_seqcount_begin() in terms of raw_read_seqcount() seqlock: Add kernel-doc for seqcount_t and seqlock_t APIs seqlock: Reorder seqcount_t and seqlock_t API definitions seqlock: seqcount_t latch: End read sections with read_seqcount_retry() seqlock: Properly format kernel-doc code samples Documentation: locking: Describe seqlock design and usage locking/qspinlock: Do not include atomic.h from qspinlock_types.h locking/atomic: Move ATOMIC_INIT into linux/types.h lockdep: Move list.h inclusion into lockdep.h locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs futex: Remove unused or redundant includes futex: Consistently use fshared as boolean futex: Remove needless goto's futex: Remove put_futex_key() rwsem: fix commas in initialisation docs: locking: Replace HTTP links with HTTPS ones ...

rculist: Add ASSERT_EXCLUSIVE_ACCESS() to __list_splice_init_rcu()

2020-06-29T19:04:48+00:00

After the sync() in __list_splice_init_rcu(), there should be no readers traversing the old list. This commit therefore enlists the help of KCSAN to verify this condition via a pair of calls to ASSERT_EXCLUSIVE_ACCESS(). Signed-off-by: Paul E. McKenney Cc: Marco Elver

rcu: Fix some kernel-doc warnings

2020-06-29T18:58:51+00:00

The current code provokes some kernel-doc warnings: ./kernel/rcu/tree.c:2915: warning: Function parameter or member 'count' not described in 'kfree_rcu_cpu' ./include/linux/rculist.h:517: warning: bad line: [@right ][node2 ... ] ./include/linux/rculist.h:2: WARNING: Unexpected indentation. This commit therefore moves the comment for "count" to the kernel-doc markup and adds a missing "*" on one kernel-doc continuation line. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Paul E. McKenney

Merge branch 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2020-06-04T20:54:34+00:00

Pull proc updates from Eric Biederman: "This has four sets of changes: - modernize proc to support multiple private instances - ensure we see the exit of each process tid exactly - remove has_group_leader_pid - use pids not tasks in posix-cpu-timers lookup Alexey updated proc so each mount of proc uses a new superblock. This allows people to actually use mount options with proc with no fear of messing up another mount of proc. Given the kernel's internal mounts of proc for things like uml this was a real problem, and resulted in Android's hidepid mount options being ignored and introducing security issues. The rest of the changes are small cleanups and fixes that came out of my work to allow this change to proc. In essence it is swapping the pids in de_thread during exec which removes a special case the code had to handle. Then updating the code to stop handling that special case" * 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: proc: proc_pid_ns takes super_block as an argument remove the no longer needed pid_alive() check in __task_pid_nr_ns() posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type posix-cpu-timers: Extend rcu_read_lock removing task_struct references signal: Remove has_group_leader_pid exec: Remove BUG_ON(has_group_leader_pid) posix-cpu-timer: Unify the now redundant code in lookup_task posix-cpu-timer: Tidy up group_leader logic in lookup_task proc: Ensure we see the exit of each process tid exactly once rculist: Add hlists_swap_heads_rcu proc: Use PIDTYPE_TGID in next_tgid Use proc_pid_ns() to get pid_namespace from the proc superblock proc: use named enums for better readability proc: use human-readable values for hidepid docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior proc: add option to mount only a pids subset proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option proc: allow to mount many instances of proc in one pid namespace proc: rename struct proc_fs_info to proc_fs_opts

rculist: Add hlists_swap_heads_rcu

2020-04-28T21:08:54+00:00

Using the struct pid to refer to two tasks in de_thread was a clever idea and ultimately too clever, as it has lead to proc_flush_task being called inconsistently. To support rectifying this add hlists_swap_heads_rcu. An hlist primitive that just swaps the hlist heads of two lists. This is exactly what is needed for exchanging the pids of two tasks. Only consideration of correctness of the code has been given, as the caller is expected to be a slowpath. Link: https://lore.kernel.org/lkml/87mu6vajnq.fsf_-_@x220.int.ebiederm.org/ Acked-by: Linus Torvalds Acked-by: Oleg Nesterov Signed-off-by: "Eric W. Biederman"

Revert "rculist: Describe variadic macro argument in a Sphinx-compatible way"

2020-04-27T18:01:16+00:00

This reverts commit f452ee096d95482892b101bde4fd037fa025d3cc. The workaround became unnecessary with commit 43756e347f21 ("scripts/kernel-doc: Add support for named variable macro arguments"). Signed-off-by: Jonathan Neuschäfer Signed-off-by: Paul E. McKenney

rculist: Add brackets around cond argument in __list_check_rcu macro

2020-02-20T23:58:23+00:00

Passing a complex lockdep condition to __list_check_rcu results in false positive lockdep splat due to incorrect expression evaluation. For example, a lockdep check condition `cond1 || cond2` is evaluated as `!cond1 || cond2 && !rcu_read_lock_any_held()` which, according to operator precedence, evaluates to `!cond1 || (cond2 && !rcu_read_lock_any_held())`. This would result in a lockdep splat when cond1 is false and cond2 is true which is logically incorrect. Signed-off-by: Amol Grover Acked-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney

rculist.h: Add list_tail_rcu()

2020-01-10T22:00:58+00:00

This patch adds the macro list_tail_rcu() and documents it. Signed-off-by: Madhuparna Bhowmik [ paulmck: Reword a bit. ] Signed-off-by: Paul E. McKenney