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  1. 12 Apr, 2022 6 commits
    • Frederic Weisbecker's avatar
      rcutorture: Call preempt_schedule() through static call/key · bd6c375b
      Frederic Weisbecker authored 
      The rcutorture test suite sometimess triggers a random scheduler
preemption call while simulating a read delay.  Unfortunately, its
direct call to preempt_schedule() bypasses the static call/key filter
used by CONFIG_PREEMPT_DYNAMIC.  This breaks the no-preempt assumption
when the dynamic preemption mode is "none".

For example, rcu_blocking_is_gp() is fooled and abbreviates grace periods
when the CPU runs in no-preempt UP mode.

Fix this by making torture_preempt_schedule() call __preempt_schedule(),
which uses the static call/key.
Reported-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      bd6c375b
    • David Vernet's avatar
      rcutorture: Add missing return and use __func__ in warning · 80dcee69
      David Vernet authored 
      The rcutorture module has an rcu_torture_writer task that repeatedly
performs writes, synchronizations, and deletes. There is a corner-case
check in rcu_torture_writer() wherein if nsynctypes is 0, a warning is
issued and the task waits to be stopped via a call to
torture_kthread_stopping() rather than performing any work.

There should be a return statement following this call to
torture_kthread_stopping(), as the intention with issuing the call to
torture_kthread_stopping() in the first place is to avoid the
rcu_torture_writer task from performing any work. Some of the work may even
be dangerous to perform, such as potentially causing a #DE due to
nsynctypes being used in a modulo operator when querying for sync updates
to issue.

This patch adds the missing return call.  As a bonus, it also fixes a
checkpatch warning that was emitted due to the WARN_ONCE() call using the
name of the function rather than __func__.
Signed-off-by: default avatarDavid Vernet <void@manifault.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      80dcee69
    • David Vernet's avatar
      rcutorture: Avoid corner-case #DE with nsynctypes check · 39b3cab9
      David Vernet authored 
      The rcutorture module is used to run torture tests that validate RCU.
rcutorture takes a variety of module parameters that configure the
functionality of the test. Amongst these parameters are the types of
synchronization mechanisms that the rcu_torture_writer and
rcu_torture_fakewriter tasks may use, and the torture_type of the run which
determines what read and sync operations are used by the various writer and
reader tasks that run throughout the test.

When the module is configured to only use sync types for which the
specified torture_type does not implement the necessary operations, we can
end up in a state where nsynctypes is 0. This is not an erroneous state,
but it currently crashes the kernel with a #DE due to nsynctypes being used
with a modulo operator in rcu_torture_fakewriter().

Here is an example of such a #DE:

$ insmod ./rcutorture.ko gp_cond=1 gp_cond_exp=0 gp_exp=0 gp_poll_exp=0
gp_normal=0 gp_poll=0 gp_poll_exp=0 verbose=9999 torture_type=trivial

...

[ 8536.525096] divide error: 0000 [#1] PREEMPT SMP PTI
[ 8536.525101] CPU: 30 PID: 392138 Comm: rcu_torture_fak Kdump: loaded Tainted: G S                5.17.0-rc1-00179-gc8c42c80febd #24
[ 8536.525105] Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020
[ 8536.525106] RIP: 0010:rcu_torture_fakewriter+0xf1/0x2d0 [rcutorture]
[ 8536.525121] Code: 00 31 d2 8d 0c f5 00 00 00 00 48 63 c9 48 f7 f1 48 85 d2 0f 84 79 ff ff ff 48 89 e7 e8 78 78 01 00 48 63 0d 29 ca 00 00 31 d2 <48> f7 f1 8b 04 95 00 05 4e a0 83 f8 06 0f 84 ad 00 00 00 7f 1f 83
[ 8536.525124] RSP: 0018:ffffc9000777fef0 EFLAGS: 00010246
[ 8536.525127] RAX: 00000000223d006e RBX: cccccccccccccccd RCX: 0000000000000000
[ 8536.525130] RDX: 0000000000000000 RSI: ffffffff824315b9 RDI: ffffc9000777fef0
[ 8536.525132] RBP: ffffc9000487bb30 R08: 0000000000000002 R09: 000000000002a580
[ 8536.525134] R10: ffffffff82c5f920 R11: 0000000000000000 R12: ffff8881a2c35d00
[ 8536.525136] R13: ffff8881540c8d00 R14: ffffffffa04d39d0 R15: 0000000000000000
[ 8536.525137] FS:  0000000000000000(0000) GS:ffff88903ff80000(0000) knlGS:0000000000000000
[ 8536.525140] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 8536.525142] CR2: 00007f839f022000 CR3: 0000000002c0a006 CR4: 00000000007706e0
[ 8536.525144] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 8536.525145] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 8536.525147] PKRU: 55555554
[ 8536.525148] Call Trace:
[ 8536.525150]  <TASK>
[ 8536.525153]  kthread+0xe8/0x110
[ 8536.525161]  ? kthread_complete_and_exit+0x20/0x20
[ 8536.525167]  ret_from_fork+0x22/0x30
[ 8536.525174]  </TASK>

The solution is to gracefully handle the case of nsynctypes being 0 in
rcu_torture_fakewriter() by not performing any work. This is already being
done in rcu_torture_writer(), though there is a missing return on that path
which will be fixed in a subsequent patch.
Signed-off-by: default avatarDavid Vernet <void@manifault.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      39b3cab9
    • Paul E. McKenney's avatar
      scftorture: Fix distribution of short handler delays · 8106bddb
      Paul E. McKenney authored 
      The scftorture test module's scf_handler() function is supposed to provide
three different distributions of short delays (including "no delay") and
one distribution of long delays, if specified by the scftorture.longwait
module parameter.  However, the second of the two non-zero-wait short delays
is disabled due to the first such delay's "goto out" not being enclosed in
the "then" clause with the "udelay()".

This commit therefore adjusts the code to provide the intended set of
delays.

Fixes: e9d338a0 ("scftorture: Add smp_call_function() torture test")
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      8106bddb
    • Paul E. McKenney's avatar
      rcutorture: Suppress debugging grace period delays during flooding · 99d6a2ac
      Paul E. McKenney authored 
      Tree RCU supports grace-period delays using the rcutree.gp_cleanup_delay,
rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot
parameters.  These delays are strictly for debugging purposes, and have
proven quite effective at exposing bugs involving race with CPU-hotplug
operations.  However, these delays can result in false positives when
used in conjunction with callback flooding, for example, those generated
by the rcutorture.fwd_progress kernel boot parameter.

This commit therefore suppresses grace-period delays while callback
flooding is in progress.
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      99d6a2ac
    • Paul E. McKenney's avatar
      torture: Add rcu_normal and rcu_expedited runs to torture.sh · b6f3c6a2
      Paul E. McKenney authored 
      Currently, the rcupdate.rcu_normal and rcupdate.rcu_expedited kernel
boot parameters are not regularly tested.  The potential addition of
polled expedited grace-period APIs increases the amount of code that is
affected by these kernel boot parameters.  This commit therefore adds a
"--do-rt" argument to torture.sh to exercise these kernel-boot options.
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      b6f3c6a2
  3. 03 Apr, 2022 8 commits
  5. 02 Apr, 2022 26 commits
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