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path: root/kernel/time/posix-timers.c
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2024-09-08treewide: Fix wrong singular form of jiffies in commentsAnna-Maria Behnsen
There are several comments all over the place, which uses a wrong singular form of jiffies. Replace 'jiffie' by 'jiffy'. No functional change. Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> # m68k Link: https://lore.kernel.org/all/20240904-devel-anna-maria-b4-timers-flseep-v1-3-e98760256370@linutronix.de
2024-07-29posix-timers: Consolidate signal queueingThomas Gleixner
Rename posix_timer_event() to posix_timer_queue_signal() as this is what the function is about. Consolidate the requeue pending and deactivation updates into that function as there is no point in doing this in all incarnations of posix timers. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2024-07-29posix-timers: Consolidate timer setupThomas Gleixner
hrtimer based and CPU timers have their own way to install the new interval and to reset overrun and signal handling related data. Create a helper function and do the same operation for all variants. This also makes the handling of the interval consistent. It's only stored when the timer is actually armed, i.e. timer->it_value != 0. Before that it was stored unconditionally for posix CPU timers and conditionally for the other posix timers. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2024-07-29posix-timers: Convert timer list to hlistThomas Gleixner
No requirement for a real list. Spare a few bytes. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2024-07-29posix-timers: Clear overrun in common_timer_set()Thomas Gleixner
Keeping the overrun count of the previous setup around is just wrong. The new setting has nothing to do with the previous one and has to start from a clean slate. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2024-07-29posix-timers: Retrieve interval in common timer_settime() codeThomas Gleixner
No point in doing this all over the place. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2023-06-18posix-timers: Refer properly to CONFIG_HIGH_RES_TIMERSLukas Bulwahn
Commit c78f261e5dcb ("posix-timers: Clarify posix_timer_fn() comments") turns an ifdef CONFIG_HIGH_RES_TIMERS into an conditional on "IS_ENABLED(CONFIG_HIGHRES_TIMERS)"; note that the new conditional refers to "HIGHRES_TIMERS" not "HIGH_RES_TIMERS" as before. Fix this typo introduced in that refactoring. Fixes: c78f261e5dcb ("posix-timers: Clarify posix_timer_fn() comments") Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20230609094643.26253-1-lukas.bulwahn@gmail.com
2023-06-18posix-timers: Polish coding style in a few placesThomas Gleixner
Make it consistent with the TIP tree documentation. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.888493625@linutronix.de
2023-06-18posix-timers: Remove pointless commentsThomas Gleixner
Documenting the obvious is just consuming space for no value. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.832240451@linutronix.de
2023-06-18posix-timers: Clarify posix_timer_fn() commentsThomas Gleixner
Make the issues vs. SIG_IGN understandable and remove the 15 years old promise that a proper solution is already on the horizon. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/874jnrdmrq.ffs@tglx
2023-06-18posix-timers: Clarify posix_timer_rearm() commentThomas Gleixner
Yet another incomprehensible piece of art. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.724863461@linutronix.de
2023-06-18posix-timers: Comment SIGEV_THREAD_ID properlyThomas Gleixner
Replace the word salad. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.672220780@linutronix.de
2023-06-18posix-timers: Add proper comments in do_timer_create()Thomas Gleixner
The comment about timer lifetime at the end of the function is misplaced and uncomprehensible. Make it understandable and put it at the right place. Add a new comment about the visibility of the new timer ID to user space. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.619897296@linutronix.de
2023-06-18posix-timers: Document nanosleep() detailsThomas Gleixner
The descriptions for common_nsleep() is wrong and common_nsleep_timens() lacks any form of comment. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.567072835@linutronix.de
2023-06-18posix-timers: Document sys_clock_settime() permissions in placeThomas Gleixner
The documentation of sys_clock_settime() permissions is at a random place and mostly word salad. Remove it and add a concise comment into sys_clock_settime(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.514700292@linutronix.de
2023-06-18posix-timers: Document sys_clock_getoverrun()Thomas Gleixner
Document the syscall in detail and with coherent sentences. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.462051641@linutronix.de
2023-06-18posix-timers: Document common_clock_get() correctlyThomas Gleixner
Replace another confusing and inaccurate set of comments. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.409169321@linutronix.de
2023-06-18posix-timers: Document sys_clock_getres() correctlyThomas Gleixner
The decades old comment about Posix clock resolution is confusing at best. Remove it and add a proper explanation to sys_clock_getres(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.356427330@linutronix.de
2023-06-18posix-timers: Split release_posix_timers()Thomas Gleixner
release_posix_timers() is called for cleaning up both hashed and unhashed timers. The cases are differentiated by an argument and the usage is hideous. Seperate the actual free path out and use it for unhashed timers. Provide a function for hashed timers. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.301432503@linutronix.de
2023-06-18posix-timers: Remove pointless irqsafe from hash_lockThomas Gleixner
All usage of hash_lock is in thread context. No point in using spin_lock_irqsave()/irqrestore() for a single usage site. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.249063953@linutronix.de
2023-06-18posix-timers: Set k_itimer:: It_signal to NULL on exit()Thomas Gleixner
Technically it's not required to set k_itimer::it_signal to NULL on exit() because there is no other thread anymore which could lookup the timer concurrently. Set it to NULL for consistency sake and add a comment to that effect. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.196462644@linutronix.de
2023-06-18posix-timers: Annotate concurrent access to k_itimer:: It_signalThomas Gleixner
k_itimer::it_signal is read lockless in the RCU protected hash lookup, but it can be written concurrently in the timer_create() and timer_delete() path. Annotate these places with READ_ONCE() and WRITE_ONCE() Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.143596887@linutronix.de
2023-06-18posix-timers: Add comments about timer lookupThomas Gleixner
Document how the timer ID validation in the hash table works. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.091081515@linutronix.de
2023-06-18posix-timers: Cleanup comments about timer ID trackingThomas Gleixner
Describe the hash table properly and remove the IDR leftover comments. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183313.038444551@linutronix.de
2023-06-18posix-timers: Clarify timer_wait_running() commentThomas Gleixner
Explain it better and add the CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y aspect for completeness. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230425183312.985681995@linutronix.de
2023-06-18posix-timers: Ensure timer ID search-loop limit is validThomas Gleixner
posix_timer_add() tries to allocate a posix timer ID by starting from the cached ID which was stored by the last successful allocation. This is done in a loop searching the ID space for a free slot one by one. The loop has to terminate when the search wrapped around to the starting point. But that's racy vs. establishing the starting point. That is read out lockless, which leads to the following problem: CPU0 CPU1 posix_timer_add() start = sig->posix_timer_id; lock(hash_lock); ... posix_timer_add() if (++sig->posix_timer_id < 0) start = sig->posix_timer_id; sig->posix_timer_id = 0; So CPU1 can observe a negative start value, i.e. -1, and the loop break never happens because the condition can never be true: if (sig->posix_timer_id == start) break; While this is unlikely to ever turn into an endless loop as the ID space is huge (INT_MAX), the racy read of the start value caught the attention of KCSAN and Dmitry unearthed that incorrectness. Rewrite it so that all id operations are under the hash lock. Reported-by: syzbot+5c54bd3eb218bb595aa9@syzkaller.appspotmail.com Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/87bkhzdn6g.ffs@tglx
2023-06-18posix-timers: Prevent RT livelock in itimer_delete()Thomas Gleixner
itimer_delete() has a retry loop when the timer is concurrently expired. On non-RT kernels this just spin-waits until the timer callback has completed, except for posix CPU timers which have HAVE_POSIX_CPU_TIMERS_TASK_WORK enabled. In that case and on RT kernels the existing task could live lock when preempting the task which does the timer delivery. Replace spin_unlock() with an invocation of timer_wait_running() to handle it the same way as the other retry loops in the posix timer code. Fixes: ec8f954a40da ("posix-timers: Use a callback for cancel synchronization on PREEMPT_RT") Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/87v8g7c50d.ffs@tglx
2023-04-21posix-cpu-timers: Implement the missing timer_wait_running callbackThomas Gleixner
For some unknown reason the introduction of the timer_wait_running callback missed to fixup posix CPU timers, which went unnoticed for almost four years. Marco reported recently that the WARN_ON() in timer_wait_running() triggers with a posix CPU timer test case. Posix CPU timers have two execution models for expiring timers depending on CONFIG_POSIX_CPU_TIMERS_TASK_WORK: 1) If not enabled, the expiry happens in hard interrupt context so spin waiting on the remote CPU is reasonably time bound. Implement an empty stub function for that case. 2) If enabled, the expiry happens in task work before returning to user space or guest mode. The expired timers are marked as firing and moved from the timer queue to a local list head with sighand lock held. Once the timers are moved, sighand lock is dropped and the expiry happens in fully preemptible context. That means the expiring task can be scheduled out, migrated, interrupted etc. So spin waiting on it is more than suboptimal. The timer wheel has a timer_wait_running() mechanism for RT, which uses a per CPU timer-base expiry lock which is held by the expiry code and the task waiting for the timer function to complete blocks on that lock. This does not work in the same way for posix CPU timers as there is no timer base and expiry for process wide timers can run on any task belonging to that process, but the concept of waiting on an expiry lock can be used too in a slightly different way: - Add a mutex to struct posix_cputimers_work. This struct is per task and used to schedule the expiry task work from the timer interrupt. - Add a task_struct pointer to struct cpu_timer which is used to store a the task which runs the expiry. That's filled in when the task moves the expired timers to the local expiry list. That's not affecting the size of the k_itimer union as there are bigger union members already - Let the task take the expiry mutex around the expiry function - Let the waiter acquire a task reference with rcu_read_lock() held and block on the expiry mutex This avoids spin-waiting on a task which might not even be on a CPU and works nicely for RT too. Fixes: ec8f954a40da ("posix-timers: Use a callback for cancel synchronization on PREEMPT_RT") Reported-by: Marco Elver <elver@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Marco Elver <elver@google.com> Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/87zg764ojw.ffs@tglx
2023-01-11timers: Prevent union confusion from unexpected restart_syscall()Jann Horn
The nanosleep syscalls use the restart_block mechanism, with a quirk: The `type` and `rmtp`/`compat_rmtp` fields are set up unconditionally on syscall entry, while the rest of the restart_block is only set up in the unlikely case that the syscall is actually interrupted by a signal (or pseudo-signal) that doesn't have a signal handler. If the restart_block was set up by a previous syscall (futex(..., FUTEX_WAIT, ...) or poll()) and hasn't been invalidated somehow since then, this will clobber some of the union fields used by futex_wait_restart() and do_restart_poll(). If userspace afterwards wrongly calls the restart_syscall syscall, futex_wait_restart()/do_restart_poll() will read struct fields that have been clobbered. This doesn't actually lead to anything particularly interesting because none of the union fields contain trusted kernel data, and futex(..., FUTEX_WAIT, ...) and poll() aren't syscalls where it makes much sense to apply seccomp filters to their arguments. So the current consequences are just of the "if userspace does bad stuff, it can damage itself, and that's not a problem" flavor. But still, it seems like a hazard for future developers, so invalidate the restart_block when partly setting it up in the nanosleep syscalls. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20230105134403.754986-1-jannh@google.com
2022-07-11fix race between exit_itimers() and /proc/pid/timersOleg Nesterov
As Chris explains, the comment above exit_itimers() is not correct, we can race with proc_timers_seq_ops. Change exit_itimers() to clear signal->posix_timers with ->siglock held. Cc: <stable@vger.kernel.org> Reported-by: chris@accessvector.net Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge misc updates from Andrew Morton: "173 patches. Subsystems affected by this series: ia64, ocfs2, block, and mm (debug, pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap, bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock, oom-kill, migration, ksm, percpu, vmstat, and madvise)" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits) mm/madvise: add MADV_WILLNEED to process_madvise() mm/vmstat: remove unneeded return value mm/vmstat: simplify the array size calculation mm/vmstat: correct some wrong comments mm/percpu,c: remove obsolete comments of pcpu_chunk_populated() selftests: vm: add COW time test for KSM pages selftests: vm: add KSM merging time test mm: KSM: fix data type selftests: vm: add KSM merging across nodes test selftests: vm: add KSM zero page merging test selftests: vm: add KSM unmerge test selftests: vm: add KSM merge test mm/migrate: correct kernel-doc notation mm: wire up syscall process_mrelease mm: introduce process_mrelease system call memblock: make memblock_find_in_range method private mm/mempolicy.c: use in_task() in mempolicy_slab_node() mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies mm/mempolicy: advertise new MPOL_PREFERRED_MANY mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY ...
2021-09-03memcg: enable accounting for posix_timers_cache slabVasily Averin
A program may create multiple interval timers using timer_create(). For each timer the kernel preallocates a "queued real-time signal", Consequently, the number of timers is limited by the RLIMIT_SIGPENDING resource limit. The allocated object is quite small, ~250 bytes, but even the default signal limits allow to consume up to 100 megabytes per user. It makes sense to account for them to limit the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/57795560-025c-267c-6b1a-dea852d95530@virtuozzo.com Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roman Gushchin <guro@fb.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Yutian Yang <nglaive@gmail.com> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-08-10posix-timers: Remove redundant initialization of variable retColin Ian King
The variable ret is being initialized with a value that is never read, it is being updated later on. The assignment is redundant and can be removed. Addresses-Coverity: ("Unused value") Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210721120147.109570-1-colin.king@canonical.com
2021-04-17posix-timers: Preserve return value in clock_adjtime32()Chen Jun
The return value on success (>= 0) is overwritten by the return value of put_old_timex32(). That works correct in the fault case, but is wrong for the success case where put_old_timex32() returns 0. Just check the return value of put_old_timex32() and return -EFAULT in case it is not zero. [ tglx: Massage changelog ] Fixes: 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to native counterparts") Signed-off-by: Chen Jun <chenjun102@huawei.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Richard Cochran <richardcochran@gmail.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210414030449.90692-1-chenjun102@huawei.com
2020-08-23treewide: Use fallthrough pseudo-keywordGustavo A. R. Silva
Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-02-17posix-timers: Pass lockdep expression to RCU listsAmol Grover
head is traversed using hlist_for_each_entry_rcu outside an RCU read-side critical section but under the protection of hash_lock. Hence, add corresponding lockdep expression to silence false-positive lockdep warnings, and harden RCU lists. [ tglx: Removed the macro and put the condition right where it's used ] Signed-off-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200216074330.GA14025@workstation-portable
2020-01-14posix-timers: Make clock_nanosleep() time namespace awareAndrei Vagin
clock_nanosleep() accepts absolute values of expiration time, if the TIMER_ABSTIME flag is set. This value is in the tasks time namespace, which has to be converted to the host time namespace. Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@openvz.org> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-18-dima@arista.com
2020-01-14hrtimers: Prepare hrtimer_nanosleep() for time namespacesAndrei Vagin
clock_nanosleep() accepts absolute values of expiration time when TIMER_ABSTIME flag is set. This absolute value is inside the task's time namespace, and has to be converted to the host's time. There is timens_ktime_to_host() helper for converting time, but it accepts ktime argument. As a preparation, make hrtimer_nanosleep() accept a clock value in ktime instead of timespec64. Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@openvz.org> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-17-dima@arista.com
2020-01-14posix-timers: Make timer_settime() time namespace awareAndrei Vagin
Wire timer_settime() syscall into time namespace virtualization. sys_timer_settime() calls the ktime->timer_set() callback. Right now, common_timer_set() is the only implementation for the callback. The user-supplied expiry value is converted from timespec64 to ktime and then timens_ktime_to_host() can be used to convert namespace's time to the host time. Inside a time namespace kernel's time differs by a fixed offset from a user-supplied time, but only absolute values (TIMER_ABSTIME) must be converted. Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@openvz.org> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-15-dima@arista.com
2020-01-14posix-clocks: Wire up clock_gettime() with timens offsetsAndrei Vagin
Adjust monotonic and boottime clocks with per-timens offsets. As the result a process inside time namespace will see timers and clocks corrected to offsets that were set when the namespace was created Note that applications usually go through vDSO to get time, which is not yet adjusted. Further changes will complete time namespace virtualisation with vDSO support. Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-12-dima@arista.com
2020-01-14posix-timers: Use clock_get_ktime() in common_timer_get()Andrei Vagin
Now, when the clock_get_ktime() callback exists, the suboptimal timespec64-based conversion can be removed from common_timer_get(). Suggested-by: Thomas Gleixner <tglx@linutronix.de> Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-11-dima@arista.com
2020-01-14posix-clocks: Introduce clock_get_ktime() callbackAndrei Vagin
The callsite in common_timer_get() has already a comment: /* * The timespec64 based conversion is suboptimal, but it's not * worth to implement yet another callback. */ kc->clock_get(timr->it_clock, &ts64); now = timespec64_to_ktime(ts64); The upcoming support for time namespaces requires to have access to: - The time in a task's time namespace for sys_clock_gettime() - The time in the root name space for common_timer_get() That adds a valid reason to finally implement a separate callback which returns the time in ktime_t format. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-10-dima@arista.com
2020-01-14posix-clocks: Rename .clock_get_timespec() callbacks accordinglyAndrei Vagin
The upcoming support for time namespaces requires to have access to: - The time in a task's time namespace for sys_clock_gettime() - The time in the root name space for common_timer_get() That adds a valid reason to finally implement a separate callback which returns the time in ktime_t format in (struct k_clock). As a preparation ground for introducing clock_get_ktime(), the original callback clock_get() was renamed into clock_get_timespec(). Reflect the renaming into the callback implementations. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-7-dima@arista.com
2020-01-14posix-clocks: Rename the clock_get() callback to clock_get_timespec()Andrei Vagin
The upcoming support for time namespaces requires to have access to: - The time in a task's time namespace for sys_clock_gettime() - The time in the root name space for common_timer_get() That adds a valid reason to finally implement a separate callback which returns the time in ktime_t format, rather than in (struct timespec). Rename the clock_get() callback to clock_get_timespec() as a preparation for introducing clock_get_ktime(). Suggested-by: Thomas Gleixner <tglx@linutronix.de> Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-6-dima@arista.com
2019-08-20hrtimer: Improve comments on handling priority inversion against softirq kthreadFrederic Weisbecker
The handling of a priority inversion between timer cancelling and a a not well defined possible preemption of softirq kthread is not very clear. Especially in the posix timers side it's unclear why there is a specific RT wait callback. All the nice explanations can be found in the initial changelog of f61eff83cec9 (hrtimer: Prepare support for PREEMPT_RT"). Extract the detailed informations from there and put it into comments. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190820132656.GC2093@lenoir
2019-08-20posix-timers: Use a callback for cancel synchronization on PREEMPT_RTThomas Gleixner
Posix timer delete retry loops are affected by the same priority inversion and live lock issues as the other timers. Provide a RT specific synchronization function which keeps a reference to the timer by holding rcu read lock to prevent the timer from being freed, dropping the timer lock and invoking the timer specific wait function via a new callback. This does not yet cover posix CPU timers because they need more special treatment on PREEMPT_RT. [ This is folded into the original attempt which did not use a callback. ] Originally-by: Anna-Maria Gleixenr <anna-maria@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lkml.kernel.org/r/20190819143801.656864506@linutronix.de
2019-08-01posix-timers: Move rcu_head out of it unionSebastian Andrzej Siewior
Timer deletion on PREEMPT_RT is prone to priority inversion and live locks. The hrtimer code has a synchronization mechanism for this. Posix CPU timers will grow one. But that mechanism cannot be invoked while holding the k_itimer lock because that can deadlock against the running timer callback. So the lock must be dropped which allows the timer to be freed. The timer free can be prevented by taking RCU readlock before dropping the lock, but because the rcu_head is part of the 'it' union a concurrent free will overwrite the hrtimer on which the task is trying to synchronize. Move the rcu_head out of the union to prevent this. [ tglx: Fixed up kernel-doc. Rewrote changelog ] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190730223828.965541887@linutronix.de
2019-08-01posix-timers: Rework cancel retry loopsThomas Gleixner
As a preparatory step for adding the PREEMPT RT specific synchronization mechanism to wait for a running timer callback, rework the timer cancel retry loops so they call a common function. This allows trivial substitution in one place. Originally-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190730223828.874901027@linutronix.de
2019-08-01posix-timers: Cleanup the flag/flags confusionThomas Gleixner
do_timer_settime() has a 'flags' argument and uses 'flag' for the interrupt flags, which is confusing at best. Rename the argument so 'flags' can be used for interrupt flags as usual. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190730223828.782664411@linutronix.de
2019-06-22posix-timers: Use spin_lock_irq() in itimer_delete()Sebastian Andrzej Siewior
itimer_delete() uses spin_lock_irqsave() to obtain a `flags' variable which can then be passed to unlock_timer(). It uses already spin_lock locking for the structure instead of lock_timer() because it has a timer which can not be removed by others at this point. The cleanup is always performed with enabled interrupts. Use spin_lock_irq() / spin_unlock_irq() so the `flags' variable can be removed. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190621143643.25649-3-bigeasy@linutronix.de