user/sven/linux.git/kernel/time/timer.c, branch v5.5-rc2

timer: Read jiffies once when forwarding base clk

2019-09-19T15:50:11Z

The timer delayed for more than 3 seconds warning was triggered during testing. Workqueue: events_unbound sched_tick_remote RIP: 0010:sched_tick_remote+0xee/0x100 ... Call Trace: process_one_work+0x18c/0x3a0 worker_thread+0x30/0x380 kthread+0x113/0x130 ret_from_fork+0x22/0x40 The reason is that the code in collect_expired_timers() uses jiffies unprotected: if (next_event > jiffies) base->clk = jiffies; As the compiler is allowed to reload the value base->clk can advance between the check and the store and in the worst case advance farther than next event. That causes the timer expiry to be delayed until the wheel pointer wraps around. Convert the code to use READ_ONCE() Fixes: 236968383cf5 ("timers: Optimize collect_expired_timers() for NOHZ") Signed-off-by: Li RongQing Signed-off-by: Liang ZhiCheng Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1568894687-14499-1-git-send-email-lirongqing@baidu.com

posix-cpu-timers: Remove tsk argument from run_posix_cpu_timers()

2019-08-21T18:27:16Z

It's always current. Don't give people wrong ideas. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/20190819143801.945469967@linutronix.de

timers: Prepare support for PREEMPT_RT

2019-08-01T18:51:22Z

When PREEMPT_RT is enabled, the soft interrupt thread can be preempted. If the soft interrupt thread is preempted in the middle of a timer callback, then calling del_timer_sync() can lead to two issues: - If the caller is on a remote CPU then it has to spin wait for the timer handler to complete. This can result in unbound priority inversion. - If the caller originates from the task which preempted the timer handler on the same CPU, then spin waiting for the timer handler to complete is never going to end. To avoid these issues, add a new lock to the timer base which is held around the execution of the timer callbacks. If del_timer_sync() detects that the timer callback is currently running, it blocks on the expiry lock. When the callback is finished, the expiry lock is dropped by the softirq thread which wakes up the waiter and the system makes progress. This addresses both the priority inversion and the life lock issues. This mechanism is not used for timers which are marked IRQSAFE as for those preemption is disabled accross the callback and therefore this situation cannot happen. The callbacks for such timers need to be individually audited for RT compliance. The same issue can happen in virtual machines when the vCPU which runs a timer callback is scheduled out. If a second vCPU of the same guest calls del_timer_sync() it will spin wait for the other vCPU to be scheduled back in. The expiry lock mechanism would avoid that. It'd be trivial to enable this when paravirt spinlocks are enabled in a guest, but it's not clear whether this is an actual problem in the wild, so for now it's an RT only mechanism. As the softirq thread can be preempted with PREEMPT_RT=y, the SMP variant of del_timer_sync() needs to be used on UP as well. [ tglx: Refactored it for mainline ] Signed-off-by: Anna-Maria Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20190726185753.832418500@linutronix.de

Merge tag 'printk-for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2019-05-07T16:18:12Z

Pull printk updates from Petr Mladek: - Allow state reset of printk_once() calls. - Prevent crashes when dereferencing invalid pointers in vsprintf(). Only the first byte is checked for simplicity. - Make vsprintf warnings consistent and inlined. - Treewide conversion of obsolete %pf, %pF to %ps, %pF printf modifiers. - Some clean up of vsprintf and test_printf code. * tag 'printk-for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: lib/vsprintf: Make function pointer_string static vsprintf: Limit the length of inlined error messages vsprintf: Avoid confusion between invalid address and value vsprintf: Prevent crash when dereferencing invalid pointers vsprintf: Consolidate handling of unknown pointer specifiers vsprintf: Factor out %pO handler as kobject_string() vsprintf: Factor out %pV handler as va_format() vsprintf: Factor out %p[iI] handler as ip_addr_string() vsprintf: Do not check address of well-known strings vsprintf: Consistent %pK handling for kptr_restrict == 0 vsprintf: Shuffle restricted_pointer() printk: Tie printk_once / printk_deferred_once into .data.once for reset treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively lib/test_printf: Switch to bitmap_zalloc()

treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively

2019-04-09T12:19:06Z

%pF and %pf are functionally equivalent to %pS and %ps conversion specifiers. The former are deprecated, therefore switch the current users to use the preferred variant. The changes have been produced by the following command: git grep -l '%p[fF]' | grep -v '^$tools\|Documentation$/' | \ while read i; do perl -i -pe 's/%pf/%ps/g; s/%pF/%pS/g;' $i; done And verifying the result. Link: http://lkml.kernel.org/r/20190325193229.23390-1-sakari.ailus@linux.intel.com Cc: Andy Shevchenko Cc: linux-arm-kernel@lists.infradead.org Cc: sparclinux@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: xen-devel@lists.xenproject.org Cc: linux-acpi@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: drbd-dev@lists.linbit.com Cc: linux-block@vger.kernel.org Cc: linux-mmc@vger.kernel.org Cc: linux-nvdimm@lists.01.org Cc: linux-pci@vger.kernel.org Cc: linux-scsi@vger.kernel.org Cc: linux-btrfs@vger.kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net Cc: linux-mm@kvack.org Cc: ceph-devel@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Sakari Ailus Acked-by: David Sterba (for btrfs) Acked-by: Mike Rapoport (for mm/memblock.c) Acked-by: Bjorn Helgaas (for drivers/pci) Acked-by: Rafael J. Wysocki Signed-off-by: Petr Mladek

timer/trace: Improve timer tracing

2019-03-24T19:29:33Z

Timers are added to the timer wheel off by one. This is required in case a timer is queued directly before incrementing jiffies to prevent early timer expiry. When reading a timer trace and relying only on the expiry time of the timer in the timer_start trace point and on the now in the timer_expiry_entry trace point, it seems that the timer fires late. With the current timer_expiry_entry trace point information only now=jiffies is printed but not the value of base->clk. This makes it impossible to draw a conclusion to the index of base->clk and makes it impossible to examine timer problems without additional trace points. Therefore add the base->clk value to the timer_expire_entry trace point, to be able to calculate the index the timer base is located at during collecting expired timers. Signed-off-by: Anna-Maria Gleixner Signed-off-by: Thomas Gleixner Cc: fweisbec@gmail.com Cc: peterz@infradead.org Cc: Steven Rostedt Link: https://lkml.kernel.org/r/20190321120921.16463-5-anna-maria@linutronix.de

timer: Move trace point to get proper index

2019-03-24T19:29:32Z

When placing the timer_start trace point before the timer wheel bucket index is calculated, the index information in the trace point is useless. It is not possible to simply move the debug_activate() call after the index calculation, because debug_object_activate() needs to be called before touching the object. Therefore split debug_activate() and move the trace point into enqueue_timer() after the new index has been calculated. The debug_object_activate() call remains at the original place. Signed-off-by: Anna-Maria Gleixner Signed-off-by: Thomas Gleixner Cc: fweisbec@gmail.com Cc: peterz@infradead.org Cc: Steven Rostedt Link: https://lkml.kernel.org/r/20190321120921.16463-3-anna-maria@linutronix.de

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-03-05T22:49:11Z

Pull RCU updates from Ingo Molnar: "The main RCU related changes in this cycle were: - Additional cleanups after RCU flavor consolidation - Grace-period forward-progress cleanups and improvements - Documentation updates - Miscellaneous fixes - spin_is_locked() conversions to lockdep - SPDX changes to RCU source and header files - SRCU updates - Torture-test updates, including nolibc updates and moving nolibc to tools/include" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits) locking/locktorture: Convert to SPDX license identifier linux/torture: Convert to SPDX license identifier torture: Convert to SPDX license identifier linux/srcu: Convert to SPDX license identifier linux/rcutree: Convert to SPDX license identifier linux/rcutiny: Convert to SPDX license identifier linux/rcu_sync: Convert to SPDX license identifier linux/rcu_segcblist: Convert to SPDX license identifier linux/rcupdate: Convert to SPDX license identifier linux/rcu_node_tree: Convert to SPDX license identifier rcu/update: Convert to SPDX license identifier rcu/tree: Convert to SPDX license identifier rcu/tiny: Convert to SPDX license identifier rcu/sync: Convert to SPDX license identifier rcu/srcu: Convert to SPDX license identifier rcu/rcutorture: Convert to SPDX license identifier rcu/rcu_segcblist: Convert to SPDX license identifier rcu/rcuperf: Convert to SPDX license identifier rcu/rcu.h: Convert to SPDX license identifier RCU/torture.txt: Remove section MODULE PARAMETERS ...

timers: Mark expected switch fall-throughs

2019-01-29T19:08:42Z

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where fall through is indeed expected. Signed-off-by: Gustavo A. R. Silva Signed-off-by: Thomas Gleixner Cc: Frederic Weisbecker Cc: John Stultz Cc: Stephen Boyd Link: https://lkml.kernel.org/r/20190123081413.GA3949@embeddedor

rcu: Rename rcu_check_callbacks() to rcu_sched_clock_irq()

2019-01-25T23:35:21Z

The name rcu_check_callbacks() arguably made sense back in the early 2000s when RCU was quite a bit simpler than it is today, but it has become quite misleading, especially with the advent of dyntick-idle and NO_HZ_FULL. The rcu_check_callbacks() function is RCU's hook into the scheduling-clock interrupt, and is now but one of many ways that callbacks get promoted to invocable state. This commit therefore changes the name to rcu_sched_clock_irq(), which is the same number of characters and clearly indicates this function's relation to the rest of the Linux kernel. In addition, for the sake of consistency, rcu_flavor_check_callbacks() is also renamed to rcu_flavor_sched_clock_irq(). While in the area, the header comments for both functions are reworked. Signed-off-by: Paul E. McKenney