crypto: Reduce preempt disabled regions, more algos
Don Estabrook reported
| kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100()
| kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2462 migrate_enable+0x17b/0x200()
| kernel: WARNING: CPU: 3 PID: 865 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100()
and his backtrace showed some crypto functions which looked fine.
The problem is the following sequence:
glue_xts_crypt_128bit()
{
blkcipher_walk_virt(); /* normal migrate_disable() */
glue_fpu_begin(); /* get atomic */
while (nbytes) {
__glue_xts_crypt_128bit();
blkcipher_walk_done(); /* with nbytes = 0, migrate_enable()
* while we are atomic */
};
glue_fpu_end() /* no longer atomic */
}
and this is why the counter get out of sync and the warning is printed.
The other problem is that we are non-preemptible between
glue_fpu_begin() and glue_fpu_end() and the latency grows. To fix this,
I shorten the FPU off region and ensure blkcipher_walk_done() is called
with preemption enabled. This might hurt the performance because we now
enable/disable the FPU state more often but we gain lower latency and
the bug is gone.
Cc: stable-rt@vger.kernel.org
Reported-by: Don Estabrook <don.estabrook@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2 files changed
