linux-toradex.git/include/linux/timer.h, branch v5.16-rc3

timer: Revert "timer: Add timer_curr_running()"

2021-05-10T23:02:44+00:00

This reverts commit dcd42591ebb8a25895b551a5297ea9c24414ba54.
The only user was RCU/nocb.

Signed-off-by: Frederic Weisbecker 
Cc: Josh Triplett 
Cc: Lai Jiangshan 
Cc: Joel Fernandes 
Cc: Neeraj Upadhyay 
Cc: Boqun Feng 
Cc: Thomas Gleixner 
Signed-off-by: Paul E. McKenney

timer: Add timer_curr_running()

2021-01-07T00:24:59+00:00

This commit adds a timer_curr_running() function that verifies that the
current code is running in the context of the specified timer's handler.

Cc: Josh Triplett 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Joel Fernandes 
Cc: Neeraj Upadhyay 
Cc: Thomas Gleixner 
Tested-by: Boqun Feng 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney

timers: Make run_local_timers() static

2020-11-16T14:20:01+00:00

No users outside of the timer code. Move the caller below this function to
avoid a pointless forward declaration.

Signed-off-by: Thomas Gleixner

timers: Mask invalid flags in do_init_timer()

2020-09-24T20:12:18+00:00

do_init_timer() accepts any combination of timer flags handed in by the
caller without a sanity check, but only TIMER_DEFFERABLE, TIMER_PINNED and
TIMER_IRQSAFE are valid.

If the supplied flags have other bits set, this could result in
malfunction. If bits are set in TIMER_CPUMASK the first timer usage could
deference a cpu base which is outside the range of possible CPUs. If
TIMER_MIGRATION is set, then the switch_timer_base() will live lock.

Prevent that with a sanity check which warns when invalid flags are
supplied and masks them out.

[ tglx: Made it WARN_ON_ONCE() and added context to the changelog ]

Signed-off-by: Qianli Zhao 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/9d79a8aa4eb56713af7379f99f062dedabcde140.1597326756.git.zhaoqianli@xiaomi.com

sysctl: pass kernel pointers to ->proc_handler

2020-04-27T06:07:40+00:00

Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig 
Acked-by: Andrey Ignatov 
Signed-off-by: Al Viro

timer: Use hlist_unhashed_lockless() in timer_pending()

2020-02-20T23:58:22+00:00

The timer_pending() function is mostly used in lockless contexts, so
Without proper annotations, KCSAN might detect a data-race [1].

Using hlist_unhashed_lockless() instead of hand-coding it seems
appropriate (as suggested by Paul E. McKenney).

[1]

BUG: KCSAN: data-race in del_timer / detach_if_pending

write to 0xffff88808697d870 of 8 bytes by task 10 on cpu 0:
 __hlist_del include/linux/list.h:764 [inline]
 detach_timer kernel/time/timer.c:815 [inline]
 detach_if_pending+0xcd/0x2d0 kernel/time/timer.c:832
 try_to_del_timer_sync+0x60/0xb0 kernel/time/timer.c:1226
 del_timer_sync+0x6b/0xa0 kernel/time/timer.c:1365
 schedule_timeout+0x2d2/0x6e0 kernel/time/timer.c:1896
 rcu_gp_fqs_loop+0x37c/0x580 kernel/rcu/tree.c:1639
 rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88808697d870 of 8 bytes by task 12060 on cpu 1:
 del_timer+0x3b/0xb0 kernel/time/timer.c:1198
 sk_stop_timer+0x25/0x60 net/core/sock.c:2845
 inet_csk_clear_xmit_timers+0x69/0xa0 net/ipv4/inet_connection_sock.c:523
 tcp_clear_xmit_timers include/net/tcp.h:606 [inline]
 tcp_v4_destroy_sock+0xa3/0x3f0 net/ipv4/tcp_ipv4.c:2096
 inet_csk_destroy_sock+0xf4/0x250 net/ipv4/inet_connection_sock.c:836
 tcp_close+0x6f3/0x970 net/ipv4/tcp.c:2497
 inet_release+0x86/0x100 net/ipv4/af_inet.c:427
 __sock_release+0x85/0x160 net/socket.c:590
 sock_close+0x24/0x30 net/socket.c:1268
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12060 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine,

Signed-off-by: Eric Dumazet 
Cc: Thomas Gleixner 
[ paulmck: Pulled in Eric's later amendments. ]
Signed-off-by: Paul E. McKenney

timers: Prepare support for PREEMPT_RT

2019-08-01T18:51:22+00:00

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

timer: Document TIMER_PINNED

2019-07-07T09:50:03+00:00

The flag hints the user that the pinned timers will always be run on a
static CPU (because that should be what "pinned" means...) but that's
not the truth, at least with the current implementation.

For example, currently if a pinned timer is set up but later mod_timer()
upon the pinned timer is invoked, mod_timer() will still try to queue the
timer on the current processor and migrate the timer if necessary.

Document it a bit with the definition of TIMER_PINNED so that all future
users will use it correctly.

Signed-off-by: Peter Xu 
Signed-off-by: Thomas Gleixner 
Cc: Marcelo Tosatti 
Cc: Luiz Capitulino 
Link: https://lkml.kernel.org/r/20190628105942.14131-1-peterx@redhat.com

timers: Remove stale struct tvec_base forward declaration

2018-04-17T15:18:04+00:00

struct tvec_base is a leftover of the original timer wheel implementation
and not longer used. Remove the forward declaration.

Signed-off-by: Liu Changcheng 
Signed-off-by: Thomas Gleixner 
Cc: akpm@linux-foundation.org
Link: https://lkml.kernel.org/r/20180412075701.GA38952@sofia

timers: Reinitialize per cpu bases on hotplug

2017-12-29T22:13:09+00:00

The timer wheel bases are not (re)initialized on CPU hotplug. That leaves
them with a potentially stale clk and next_expiry valuem, which can cause
trouble then the CPU is plugged.

Add a prepare callback which forwards the clock, sets next_expiry to far in
the future and reset the control flags to a known state.

Set base->must_forward_clk so the first timer which is queued will try to
forward the clock to current jiffies.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Reported-by: Paul E. McKenney 
Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: Sebastian Siewior 
Cc: Anna-Maria Gleixner 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos