Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable
flat view
From: Rafael J. Wysocki <hidden>
Date: 2016-06-27 01:08:00
Also in:
linux-acpi, lkml
On Sunday, June 26, 2016 12:28:48 AM Chen Yu wrote:
quoted hunk ↗ jump to hunk
Previously we saw warning during resume on some platforms, which use acpi-cpufreq: smpboot: Booting Node 0 Processor 3 APIC 0x5 cache: parent cpu3 should not be sleeping CPU3 is up ACPI: Waking up from system sleep state S3 WARNING: CPU: 0 PID: 12546 at drivers/cpufreq/cpufreq.c:2173 Call Trace: [<ffffffff81311d95>] dump_stack+0x5c/0x77 [<ffffffff8107aef4>] __warn+0xc4/0xe0 [<ffffffff8148c13e>] cpufreq_update_policy+0xfe/0x150 [<ffffffff8148c190>] cpufreq_update_policy+0x150/0x150 [<ffffffffc03e42ef>] acpi_processor_notify+0x51/0xdc [processor] [<ffffffff813b0d24>] acpi_ev_notify_dispatch+0x3c/0x55 [<ffffffff81399613>] acpi_os_execute_deferred+0x10/0x1a [<ffffffff81093ffb>] process_one_work+0x14b/0x400 [<ffffffff81094aa5>] worker_thread+0x65/0x4a0 [<ffffffff81094a40>] rescuer_thread+0x340/0x340 [<ffffffff81099dbf>] kthread+0xdf/0x100 [<ffffffff815c7ee2>] ret_from_fork+0x22/0x40 [<ffffffff81099ce0>] kthread_park+0x50/0x50 This is because this platforms tries to notify the processor to reevaluate the _PPC object in _WAK, however at that time the cpufreq driver's resume has not been invoked yet, thus cpufreq_update_current_freq returns zero because of cpufreq_suspended = true, which caused the warning. Actually it should be unnecessary to care the update request at that moment, so remove the warning and change the return value to -EAGAIN for invokers. Reported-and-tested-by: BzukTuk <redacted> Signed-off-by: Chen Yu <yu.c.chen@intel.com> --- drivers/cpufreq/cpufreq.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 9009295..67a3aa1 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c@@ -2262,8 +2262,11 @@ int cpufreq_update_policy(unsigned int cpu) */ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { new_policy.cur = cpufreq_update_current_freq(policy); - if (WARN_ON(!new_policy.cur)) { - ret = -EIO; + if (!new_policy.cur) { + if (WARN_ON(!cpufreq_suspended))
If we know that cpufreq is suspended, there's no reason to call cpufreq_update_current_freq() at all here.
quoted hunk ↗ jump to hunk
+ ret = -EIO; + else + ret = -EAGAIN; goto unlock; } }
Moreover, cpufreq_update_current_freq() has only two callers and the other one already checks cpufreq_suspended before invoking it, so what about the patch below instead? --- drivers/cpufreq/cpufreq.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) Index: linux-pm/drivers/cpufreq/cpufreq.c ===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c@@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre { unsigned int new_freq; - if (cpufreq_suspended) - return 0; - new_freq = cpufreq_driver->get(policy->cpu); if (!new_freq) return 0;
@@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c * -> ask driver for current freq and notify governors about a change */ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { + if (cpufreq_suspended) { + ret = -EAGAIN; + goto unlock; + } new_policy.cur = cpufreq_update_current_freq(policy); if (WARN_ON(!new_policy.cur)) { ret = -EIO;