linux.git/kernel/scftorture.c, branch v6.18.21

scftorture: Handle NULL argument passed to scf_add_to_free_list().

2024-11-15T00:09:51+00:00

Dan reported that after the rework the newly introduced
scf_add_to_free_list() may get a NULL pointer passed. This replaced
kfree() which was fine with a NULL pointer but scf_add_to_free_list()
isn't.

Let scf_add_to_free_list() handle NULL pointer.

Reported-by: Dan Carpenter 
Closes: https://lore.kernel.org/all/2375aa2c-3248-4ffa-b9b0-f0a24c50f237@stanley.mountain
Fixes: 4788c861ad7e9 ("scftorture: Use a lock-less list to free memory.")
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Paul E. McKenney

scftorture: Use a lock-less list to free memory.

2024-11-09T17:00:46+00:00

scf_handler() is used as a SMP function call. This function is always
invoked in IRQ-context even with forced-threading enabled. This function
frees memory which not allowed on PREEMPT_RT because the locking
underneath is using sleeping locks.

Add a per-CPU scf_free_pool where each SMP functions adds its memory to
be freed. This memory is then freed by scftorture_invoker() on each
iteration. On the majority of invocations the number of items is less
than five. If the thread sleeps/ gets delayed the number exceed 350 but
did not reach 400 in testing. These were the spikes during testing.
The bulk free of 64 pointers at once should improve the give-back if the
list grows. The list size is ~1.3 items per invocations.

Having one global scf_free_pool with one cleaning thread let the list
grow to over 10.000 items with 32 CPUs (again, spikes not the average)
especially if the CPU went to sleep. The per-CPU part looks like a good
compromise.

Reported-by: "Paul E. McKenney" 
Closes: https://lore.kernel.org/lkml/41619255-cdc2-4573-a360-7794fc3614f7@paulmck-laptop/
Tested-by: Paul E. McKenney 
Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Boqun Feng 
Tested-by: Boqun Feng 
Signed-off-by: Paul E. McKenney

scftorture: Move memory allocation outside of preempt_disable region.

2024-11-09T17:00:46+00:00

Memory allocations can not happen within regions with explicit disabled
preemption PREEMPT_RT. The problem is that the locking structures
underneath are sleeping locks.

Move the memory allocation outside of the preempt-disabled section. Keep
the GFP_ATOMIC for the allocation to behave like a "ememergncy
allocation".

Tested-by: Paul E. McKenney 
Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Boqun Feng 
Tested-by: Boqun Feng 
Signed-off-by: Paul E. McKenney

scftorture: Wait until scf_cleanup_handler() completes.

2024-11-09T17:00:46+00:00

The smp_call_function() needs to be invoked with the wait flag set to
wait until scf_cleanup_handler() is done. This ensures that all SMP
function calls, that have been queued earlier, complete at this point.

Tested-by: Paul E. McKenney 
Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Boqun Feng 
Tested-by: Boqun Feng 
Signed-off-by: Paul E. McKenney

scftorture: Avoid additional div operation.

2024-11-09T17:00:46+00:00

Replace "scfp->cpu % nr_cpu_ids" with "cpu". This has been computed
earlier.

Tested-by: Paul E. McKenney 
Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Boqun Feng 
Tested-by: Boqun Feng 
Signed-off-by: Paul E. McKenney

scftorture: Make torture_type static

2024-05-30T22:31:51+00:00

Fix the 'make C=1' warning:
kernel/scftorture.c:71:6: warning: symbol 'torture_type' was not declared. Should it be static?

Signed-off-by: Jeff Johnson 
Signed-off-by: Paul E. McKenney

scftorture: Add MODULE_DESCRIPTION()

2024-05-30T22:31:45+00:00

Fix the 'make W=1' warning:
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/scftorture.o

Signed-off-by: Jeff Johnson 
Signed-off-by: Paul E. McKenney

scftorture: Pause testing after memory-allocation failure

2023-07-14T22:02:57+00:00

The scftorture test can quickly execute a large number of calls to no-wait
smp_call_function(), each of which holds a block of memory until the
corresponding handler is invoked.  Especially when the longwait module
parameter is specified, this can chew up an arbitrarily large amount
of memory.  This commit therefore blocks after each memory-allocation
failure, with the duration a function of longwait.

Signed-off-by: Paul E. McKenney

scftorture: Forgive memory-allocation failure if KASAN

2023-07-14T22:02:57+00:00

Kernels built with CONFIG_KASAN=y quarantine newly freed memory in order
to better detect use-after-free errors.  However, this can exhaust memory
more quickly in allocator-heavy tests, which can result in spurious
scftorture failure.  This commit therefore forgives memory-allocation
failure in kernels built with CONFIG_KASAN=y, but continues counting
the errors for use in detailed test-result analyses.

Signed-off-by: Paul E. McKenney

scftorture: Fix distribution of short handler delays

2022-04-12T00:07:29+00:00

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: e9d338a0b179 ("scftorture: Add smp_call_function() torture test")
Signed-off-by: Paul E. McKenney