rcutorture: Fix invalid context warning when enable srcu barrier testing

[ Upstream commit 668c0406d887467d53f8fe79261dda1d22d5b671 ]

When the torture_type is set srcu or srcud and cb_barrier is
no

rcutorture: Fix invalid context warning when enable srcu barrier testing

[ Upstream commit 668c0406d887467d53f8fe79261dda1d22d5b671 ]

When the torture_type is set srcu or srcud and cb_barrier is
non-zero, running the rcutorture test will trigger the
following warning:

[ 163.910989][ C1] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
[ 163.910994][ C1] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
[ 163.910999][ C1] preempt_count: 10001, expected: 0
[ 163.911002][ C1] RCU nest depth: 0, expected: 0
[ 163.911005][ C1] INFO: lockdep is turned off.
[ 163.911007][ C1] irq event stamp: 30964
[ 163.911010][ C1] hardirqs last enabled at (30963): [<ffffffffabc7df52>] do_idle+0x362/0x500
[ 163.911018][ C1] hardirqs last disabled at (30964): [<ffffffffae616eff>] sysvec_call_function_single+0xf/0xd0
[ 163.911025][ C1] softirqs last enabled at (0): [<ffffffffabb6475f>] copy_process+0x16ff/0x6580
[ 163.911033][ C1] softirqs last disabled at (0): [<0000000000000000>] 0x0
[ 163.911038][ C1] Preemption disabled at:
[ 163.911039][ C1] [<ffffffffacf1964b>] stack_depot_save_flags+0x24b/0x6c0
[ 163.911063][ C1] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 6.8.0-rc4-rt4-yocto-preempt-rt+ #3 1e39aa9a737dd024a3275c4f835a872f673a7d3a
[ 163.911071][ C1] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[ 163.911075][ C1] Call Trace:
[ 163.911078][ C1] <IRQ>
[ 163.911080][ C1] dump_stack_lvl+0x88/0xd0
[ 163.911089][ C1] dump_stack+0x10/0x20
[ 163.911095][ C1] __might_resched+0x36f/0x530
[ 163.911105][ C1] rt_spin_lock+0x82/0x1c0
[ 163.911112][ C1] spin_lock_irqsave_ssp_contention+0xb8/0x100
[ 163.911121][ C1] srcu_gp_start_if_needed+0x782/0xf00
[ 163.911128][ C1] ? _raw_spin_unlock_irqrestore+0x46/0x70
[ 163.911136][ C1] ? debug_object_active_state+0x336/0x470
[ 163.911148][ C1] ? __pfx_srcu_gp_start_if_needed+0x10/0x10
[ 163.911156][ C1] ? __pfx_lock_release+0x10/0x10
[ 163.911165][ C1] ? __pfx_rcu_torture_barrier_cbf+0x10/0x10
[ 163.911188][ C1] __call_srcu+0x9f/0xe0
[ 163.911196][ C1] call_srcu+0x13/0x20
[ 163.911201][ C1] srcu_torture_call+0x1b/0x30
[ 163.911224][ C1] rcu_torture_barrier1cb+0x4a/0x60
[ 163.911247][ C1] __flush_smp_call_function_queue+0x267/0xca0
[ 163.911256][ C1] ? __pfx_rcu_torture_barrier1cb+0x10/0x10
[ 163.911281][ C1] generic_smp_call_function_single_interrupt+0x13/0x20
[ 163.911288][ C1] __sysvec_call_function_single+0x7d/0x280
[ 163.911295][ C1] sysvec_call_function_single+0x93/0xd0
[ 163.911302][ C1] </IRQ>
[ 163.911304][ C1] <TASK>
[ 163.911308][ C1] asm_sysvec_call_function_single+0x1b/0x20
[ 163.911313][ C1] RIP: 0010:default_idle+0x17/0x20
[ 163.911326][ C1] RSP: 0018:ffff888001997dc8 EFLAGS: 00000246
[ 163.911333][ C1] RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffffae618b51
[ 163.911337][ C1] RDX: 0000000000000000 RSI: ffffffffaea80920 RDI: ffffffffaec2de80
[ 163.911342][ C1] RBP: ffff888001997dc8 R08: 0000000000000001 R09: ffffed100d740cad
[ 163.911346][ C1] R10: ffffed100d740cac R11: ffff88806ba06563 R12: 0000000000000001
[ 163.911350][ C1] R13: ffffffffafe460c0 R14: ffffffffafe460c0 R15: 0000000000000000
[ 163.911358][ C1] ? ct_kernel_exit.constprop.3+0x121/0x160
[ 163.911369][ C1] ? lockdep_hardirqs_on+0xc4/0x150
[ 163.911376][ C1] arch_cpu_idle+0x9/0x10
[ 163.911383][ C1] default_idle_call+0x7a/0xb0
[ 163.911390][ C1] do_idle+0x362/0x500
[ 163.911398][ C1] ? __pfx_do_idle+0x10/0x10
[ 163.911404][ C1] ? complete_with_flags+0x8b/0xb0
[ 163.911416][ C1] cpu_startup_entry+0x58/0x70
[ 163.911423][ C1] start_secondary+0x221/0x280
[ 163.911430][ C1] ? __pfx_start_secondary+0x10/0x10
[ 163.911440][ C1] secondary_startup_64_no_verify+0x17f/0x18b
[ 163.911455][ C1] </TASK>

This commit therefore use smp_call_on_cpu() instead of
smp_call_function_single(), make rcu_torture_barrier1cb() invoked
happens on task-context.

Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

rcutorture: Make stall-tasks directly exit when rcutorture tests end

[ Upstream commit 431315a563015f259b28e34c5842f6166439e969 ]

When the rcutorture tests start to exit, the rcu_torture_cleanup()

rcutorture: Make stall-tasks directly exit when rcutorture tests end

[ Upstream commit 431315a563015f259b28e34c5842f6166439e969 ]

When the rcutorture tests start to exit, the rcu_torture_cleanup() is
invoked to stop kthreads and release resources, if the stall-task
kthreads exist, cpu-stall has started and the rcutorture.stall_cpu
is set to a larger value, the rcu_torture_cleanup() will be blocked
for a long time and the hung-task may occur, this commit therefore
add kthread_should_stop() to the loop of cpu-stall operation, when
rcutorture tests ends, no need to wait for cpu-stall to end, exit
directly.

Use the following command to test:

insmod rcutorture.ko torture_type=srcu fwd_progress=0 stat_interval=4
stall_cpu_block=1 stall_cpu=200 stall_cpu_holdoff=10 read_exit_burst=0
object_debug=1
rmmod rcutorture

[15361.918610] INFO: task rmmod:878 blocked for more than 122 seconds.
[15361.918613] Tainted: G W
6.8.0-rc2-yoctodev-standard+ #25
[15361.918615] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[15361.918616] task:rmmod state:D stack:0 pid:878
tgid:878 ppid:773 flags:0x00004002
[15361.918621] Call Trace:
[15361.918623] <TASK>
[15361.918626] __schedule+0xc0d/0x28f0
[15361.918631] ? __pfx___schedule+0x10/0x10
[15361.918635] ? rcu_is_watching+0x19/0xb0
[15361.918638] ? schedule+0x1f6/0x290
[15361.918642] ? __pfx_lock_release+0x10/0x10
[15361.918645] ? schedule+0xc9/0x290
[15361.918648] ? schedule+0xc9/0x290
[15361.918653] ? trace_preempt_off+0x54/0x100
[15361.918657] ? schedule+0xc9/0x290
[15361.918661] schedule+0xd0/0x290
[15361.918665] schedule_timeout+0x56d/0x7d0
[15361.918669] ? debug_smp_processor_id+0x1b/0x30
[15361.918672] ? rcu_is_watching+0x19/0xb0
[15361.918676] ? __pfx_schedule_timeout+0x10/0x10
[15361.918679] ? debug_smp_processor_id+0x1b/0x30
[15361.918683] ? rcu_is_watching+0x19/0xb0
[15361.918686] ? wait_for_completion+0x179/0x4c0
[15361.918690] ? __pfx_lock_release+0x10/0x10
[15361.918693] ? __kasan_check_write+0x18/0x20
[15361.918696] ? wait_for_completion+0x9d/0x4c0
[15361.918700] ? _raw_spin_unlock_irq+0x36/0x50
[15361.918703] ? wait_for_completion+0x179/0x4c0
[15361.918707] ? _raw_spin_unlock_irq+0x36/0x50
[15361.918710] ? wait_for_completion+0x179/0x4c0
[15361.918714] ? trace_preempt_on+0x54/0x100
[15361.918718] ? wait_for_completion+0x179/0x4c0
[15361.918723] wait_for_completion+0x181/0x4c0
[15361.918728] ? __pfx_wait_for_completion+0x10/0x10
[15361.918738] kthread_stop+0x152/0x470
[15361.918742] _torture_stop_kthread+0x44/0xc0 [torture
7af7f9cbba28271a10503b653f9e05d518fbc8c3]
[15361.918752] rcu_torture_cleanup+0x2ac/0xe90 [rcutorture
f2cb1f556ee7956270927183c4c2c7749a336529]
[15361.918766] ? __pfx_rcu_torture_cleanup+0x10/0x10 [rcutorture
f2cb1f556ee7956270927183c4c2c7749a336529]
[15361.918777] ? __kasan_check_write+0x18/0x20
[15361.918781] ? __mutex_unlock_slowpath+0x17c/0x670
[15361.918789] ? __might_fault+0xcd/0x180
[15361.918793] ? find_module_all+0x104/0x1d0
[15361.918799] __x64_sys_delete_module+0x2a4/0x3f0
[15361.918803] ? __pfx___x64_sys_delete_module+0x10/0x10
[15361.918807] ? syscall_exit_to_user_mode+0x149/0x280

Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

rcutorture: Fix rcu_torture_one_read() pipe_count overflow comment

[ Upstream commit 8b9b443fa860276822b25057cb3ff3b28734dec0 ]

The "pipe_count > RCU_TORTURE_PIPE_LEN" check has a comment saying "S

rcutorture: Fix rcu_torture_one_read() pipe_count overflow comment

[ Upstream commit 8b9b443fa860276822b25057cb3ff3b28734dec0 ]

The "pipe_count > RCU_TORTURE_PIPE_LEN" check has a comment saying "Should
not happen, but...". This is only true when testing an RCU whose grace
periods are always long enough. This commit therefore fixes this comment.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/lkml/CAHk-=wi7rJ-eGq+xaxVfzFEgbL9tdf6Kc8Z89rCpfcQOKm74Tw@mail.gmail.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

rcutorture: Stop right-shifting torture_random() return values

Now that torture_random() uses swahw32(), its callers no longer see
not-so-random low-order bits, as these are now swapped up into the

rcutorture: Stop right-shifting torture_random() return values

Now that torture_random() uses swahw32(), its callers no longer see
not-so-random low-order bits, as these are now swapped up into the upper
16 bits of the torture_random() function's return value. This commit
therefore removes the right-shifting of torture_random() return values.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcutorture: Dump grace-period state upon rtort_pipe_count incidents

The rtort_pipe_count WARN() indicates that grace periods were unable
to invoke all callbacks during a stutter_wait() interval. Bu

rcutorture: Dump grace-period state upon rtort_pipe_count incidents

The rtort_pipe_count WARN() indicates that grace periods were unable
to invoke all callbacks during a stutter_wait() interval. But it is
sometimes helpful to have a bit more information as to why. This commit
therefore invokes show_rcu_gp_kthreads() immediately before that WARN()
in order to dump out some relevant information.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcutorture: Add RCU Tasks Trace and SRCU deadlock scenarios

Add a test number 3 that creates deadlock cycles involving one RCU
Tasks Trace step and L-1 SRCU steps. Please note that lockdep will not

rcutorture: Add RCU Tasks Trace and SRCU deadlock scenarios

Add a test number 3 that creates deadlock cycles involving one RCU
Tasks Trace step and L-1 SRCU steps. Please note that lockdep will not
detect these deadlocks until synchronize_rcu_tasks_trace() is marked
with lockdep's new "sync" annotation, which will probably not happen
until some time after these markings prove their worth on SRCU.

Please note that these tests are available only in kernels built with
CONFIG_TASKS_TRACE_RCU=y.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...

rcutorture: Add SRCU deadlock scenarios

In order to test the new SRCU-lockdep functionality, this commit adds
an rcutorture.test_srcu_lockdep module parameter that, when non-zero,
selects an SRCU de

rcutorture: Add SRCU deadlock scenarios

In order to test the new SRCU-lockdep functionality, this commit adds
an rcutorture.test_srcu_lockdep module parameter that, when non-zero,
selects an SRCU deadlock scenario to execute. This parameter is a
five-digit number formatted as DNNL, where "D" is 1 to force a deadlock
and 0 to avoid doing so; "NN" is the test number, 0 for SRCU-based, 1
for SRCU/mutex-based, and 2 for SRCU/rwsem-based; and "L" is the number
of steps in the deadlock cycle.

Note that rcutorture.test_srcu_lockdep=1 will also force a hard hang.

If a non-zero value of rcutorture.test_srcu_lockdep does not select a
deadlock scenario, a console message is printed and testing continues.

[ paulmck: Apply kernel test robot feedback, add rwsem support. ]
[ paulmck: Apply Dan Carpenter feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...

rcutorture: Create nocb kthreads only when testing rcu in CONFIG_RCU_NOCB_CPU=y kernels

Given a non-zero rcutorture.nocbs_nthreads module parameter, the specified
number of nocb kthreads will be cre

rcutorture: Create nocb kthreads only when testing rcu in CONFIG_RCU_NOCB_CPU=y kernels

Given a non-zero rcutorture.nocbs_nthreads module parameter, the specified
number of nocb kthreads will be created, regardless of whether or not
the RCU implementation under test is capable of offloading callbacks.
Please note that even vanilla RCU is incapable of offloading in kernels
built with CONFIG_RCU_NOCB_CPU=n. And when the RCU implementation is
incapable of offloading callbacks, there is no point in creating those
kthreads.

This commit therefore checks the cur_ops.torture_type module parameter and
CONFIG_RCU_NOCB_CPU Kconfig option in order to avoid creating unnecessary
nocb tasks.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ boqun: Fix checkpatch warning ]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...

rcutorture: Eliminate variable n_rcu_torture_boost_rterror

After commit 8b700983de82 ("sched: Remove sched_set_*() return value"),
this variable is not used anymore. So eliminate it entirely.

Signe

rcutorture: Eliminate variable n_rcu_torture_boost_rterror

After commit 8b700983de82 ("sched: Remove sched_set_*() return value"),
this variable is not used anymore. So eliminate it entirely.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...

rcutorture: Add test_nmis module parameter

This commit adds a test_nmis module parameter to generate the
specified number of NMI stack backtraces 15 seconds apart. This module
parameter can be used

rcutorture: Add test_nmis module parameter

This commit adds a test_nmis module parameter to generate the
specified number of NMI stack backtraces 15 seconds apart. This module
parameter can be used to test NMI delivery and accompanying diagnostics.
Note that this parameter is ignored when rcutorture is a module rather
than built into the kernel. This could be changed with the addition of
an EXPORT_SYMBOL_GPL().

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...

rcutorture: Drop sparse lock-acquisition annotations

The sparse __acquires() and __releases() annotations provide very
little value. The argument is ignored, so sparse cannot tell the
differences b

rcutorture: Drop sparse lock-acquisition annotations

The sparse __acquires() and __releases() annotations provide very
little value. The argument is ignored, so sparse cannot tell the
differences between acquiring one lock and releasing another on the one
hand and acquiring and releasing a given lock on the other. In addition,
lockdep annotations provide much more precision, for but one example,
actually knowing which lock is held.

This commit therefore removes the __acquires() and __releases()
annotations from rcutorture.

Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcu/rcutorture: Use call_rcu_hurry() where needed

call_rcu() changes to save power will change the behavior of rcutorture
tests. Use the call_rcu_hurry() API instead which reverts to the old
behavio

rcu/rcutorture: Use call_rcu_hurry() where needed

call_rcu() changes to save power will change the behavior of rcutorture
tests. Use the call_rcu_hurry() API instead which reverts to the old
behavior.

[ paulmck: Apply s/call_rcu_flush/call_rcu_hurry/ feedback from Tejun Heo. ]

Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe()

On strict load-store architectures, the use of this_cpu_inc() by
srcu_read_lock() and srcu_read_unlock() is not NMI-safe in TR

srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe()

On strict load-store architectures, the use of this_cpu_inc() by
srcu_read_lock() and srcu_read_unlock() is not NMI-safe in TREE SRCU.
To see this suppose that an NMI arrives in the middle of srcu_read_lock(),
just after it has read ->srcu_lock_count, but before it has written
the incremented value back to memory. If that NMI handler also does
srcu_read_lock() and srcu_read_lock() on that same srcu_struct structure,
then upon return from that NMI handler, the interrupted srcu_read_lock()
will overwrite the NMI handler's update to ->srcu_lock_count, but
leave unchanged the NMI handler's update by srcu_read_unlock() to
->srcu_unlock_count.

This can result in a too-short SRCU grace period, which can in turn
result in arbitrary memory corruption.

If the NMI handler instead interrupts the srcu_read_unlock(), this
can result in eternal SRCU grace periods, which is not much better.

This commit therefore creates a pair of new srcu_read_lock_nmisafe()
and srcu_read_unlock_nmisafe() functions, which allow SRCU readers in
both NMI handlers and in process and IRQ context. It is bad practice
to mix the existing and the new _nmisafe() primitives on the same
srcu_struct structure. Use one set or the other, not both.

Just to underline that "bad practice" point, using srcu_read_lock() at
process level and srcu_read_lock_nmisafe() in your NMI handler will not,
repeat NOT, work. If you do not immediately understand why this is the
case, please review the earlier paragraphs in this commit log.

[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Apply feedback from Randy Dunlap. ]
[ paulmck: Apply feedback from John Ogness. ]
[ paulmck: Apply feedback from Frederic Weisbecker. ]

Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>

show more ...

rcutorture: Verify NUM_ACTIVE_RCU_POLL_OLDSTATE

This commit adds code to the RTWS_POLL_GET case of rcu_torture_writer()
to verify that the value of NUM_ACTIVE_RCU_POLL_OLDSTATE is sufficiently
large

rcutorture: Verify NUM_ACTIVE_RCU_POLL_OLDSTATE

This commit adds code to the RTWS_POLL_GET case of rcu_torture_writer()
to verify that the value of NUM_ACTIVE_RCU_POLL_OLDSTATE is sufficiently
large

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcutorture: Verify NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE

This commit adds code to the RTWS_POLL_GET_FULL case
of rcu_torture_writer() to verify that the value of
NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE is suf

rcutorture: Verify NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE

This commit adds code to the RTWS_POLL_GET_FULL case
of rcu_torture_writer() to verify that the value of
NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE is sufficiently large.

[ paulmck: Fix whitespace issue located by checkpatch.pl. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcutorture: Use the barrier operation specified by cur_ops

The rcutorture_oom_notify() function unconditionally invokes
rcu_barrier(), which is OK when the rcutorture.torture_type value is
"rcu", bu

rcutorture: Use the barrier operation specified by cur_ops

The rcutorture_oom_notify() function unconditionally invokes
rcu_barrier(), which is OK when the rcutorture.torture_type value is
"rcu", but unhelpful otherwise. The purpose of these barrier calls is to
wait for all outstanding callback-flooding callbacks to be invoked before
cleaning up their data. Using the wrong barrier function therefore
risks arbitrary memory corruption. Thus, this commit changes these
rcu_barrier() calls into cur_ops->cb_barrier() to make things work when
torturing non-vanilla flavors of RCU.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcutorture: Make "srcud" option also test polled grace-period API

This commit brings the "srcud" (dynamically allocated) SRCU test in line
with the "srcu" (statically allocated) test, so that both t

rcutorture: Make "srcud" option also test polled grace-period API

This commit brings the "srcud" (dynamically allocated) SRCU test in line
with the "srcu" (statically allocated) test, so that both test the full
SRCU polled grace-period API.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...

rcutorture: Limit read-side polling-API testing

RCU's polled grace-period API is reasonably lightweight, but still
contains heavyweight memory barriers. This commit therefore limits
testing of this

rcutorture: Limit read-side polling-API testing

RCU's polled grace-period API is reasonably lightweight, but still
contains heavyweight memory barriers. This commit therefore limits
testing of this API from rcutorture's readers in order to avoid the
false negatives that these heavyweight operations could provoke.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcutorture: Expand rcu_torture_write_types() first "if" statement

This commit expands the rcu_torture_write_types() function's first "if"
condition and body, placing one element per line, in order t

rcutorture: Expand rcu_torture_write_types() first "if" statement

This commit expands the rcu_torture_write_types() function's first "if"
condition and body, placing one element per line, in order to make the
compiler's error messages more helpful.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcutorture: Use 1-suffixed variable in rcu_torture_write_types() check

This commit changes the use of gp_poll_exp to gp_poll_exp1 in the first
check in rcu_torture_write_types(). No functional effe

rcutorture: Use 1-suffixed variable in rcu_torture_write_types() check

This commit changes the use of gp_poll_exp to gp_poll_exp1 in the first
check in rcu_torture_write_types(). No functional effect, but consistency
is a good thing.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcutorture: Adjust rcu_poll_need_2gp() for rcu_gp_oldstate field removal

Now that rcu_gp_oldstate can accurately track both normal and
expedited grace periods regardless of system state, rcutorture'

rcutorture: Adjust rcu_poll_need_2gp() for rcu_gp_oldstate field removal

Now that rcu_gp_oldstate can accurately track both normal and
expedited grace periods regardless of system state, rcutorture's
rcu_poll_need_2gp() function need only call for a second grace period
for the old single-unsigned-long grace-period polling APIs
This commit therefore adjusts rcu_poll_need_2gp() accordingly.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcu: Add full-sized polling for cond_sync_exp_full()

The cond_synchronize_rcu_expedited() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which cons

rcu: Add full-sized polling for cond_sync_exp_full()

The cond_synchronize_rcu_expedited() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.

This commit therefore adds yet another member of the full-state RCU
grace-period polling API, which is the cond_synchronize_rcu_exp_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcu: Add full-sized polling for cond_sync_full()

The cond_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage,

rcu: Add full-sized polling for cond_sync_full()

The cond_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.

This commit therefore adds yet another member of the full-state RCU
grace-period polling API, which is the cond_synchronize_rcu_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.

[ paulmck: Apply feedback from kernel test robot and Julia Lawall. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcu: Add full-sized polling for start_poll_expedited()

The start_poll_synchronize_rcu_expedited() API compresses the combined
expedited and normal grace-period states into a single unsigned long,
wh

rcu: Add full-sized polling for start_poll_expedited()

The start_poll_synchronize_rcu_expedited() API compresses the combined
expedited and normal grace-period states into a single unsigned long,
which conserves storage, but can miss grace periods in certain cases
involving overlapping normal and expedited grace periods. Missing the
occasional grace period is usually not a problem, but there are use
cases that care about each and every grace period.

This commit therefore adds yet another member of the
full-state RCU grace-period polling API, which is the
start_poll_synchronize_rcu_expedited_full() function. This uses up to
three times the storage (rcu_gp_oldstate structure instead of unsigned
long), but is guaranteed not to miss grace periods.

[ paulmck: Apply feedback from kernel test robot and Julia Lawall. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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rcu: Add full-sized polling for start_poll()

The start_poll_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storag

rcu: Add full-sized polling for start_poll()

The start_poll_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.

This commit therefore adds the next member of the full-state RCU
grace-period polling API, namely the start_poll_synchronize_rcu_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

show more ...