On 17/08/2023 09:41, hejunhao wrote:
Hi Anshuman Khandual,
On 2023/8/17 15:13, Anshuman Khandual wrote:
Hello Junhao,
On 8/16/23 19:40, Suzuki K Poulose wrote:
From: Junhao He hejunhao3@huawei.com
smp_call_function_single() will allocate an IPI interrupt vector to the target processor and send a function call request to the interrupt vector. After the target processor receives the IPI interrupt, it will execute arm_trbe_remove_coresight_cpu() call request in the interrupt handler.
According to the device_unregister() stack information, if other process is useing the device, the down_write() may sleep, and trigger deadlocks or unexpected errors.
arm_trbe_remove_coresight_cpu coresight_unregister device_unregister device_del kobject_del __kobject_del sysfs_remove_dir kernfs_remove down_write ---------> it may sleep
But how did you really detect this problem ? Does this show up as an warning when you enable lockdep debug ? OR it really happened during a real workload execution followed by TRBE module unload. Although the problem seems plausible (which needs fixing), just wondering how did we trigger this.
Yes, it really happened during a real workload.
If the TRBE driver is loaded and unloaded cyclically. the test script following:
for ((i=0;i<99999;i++)) do insmod coresight-trbe.ko; rmmod coresight-trbe.ko; echo "loop $i"; done
The kernel will report a panic.
I wonder how easy it would be to add a kselftest to do this with all of the Coresight modules. Because we also had a problem with bad reference counting preventing an unload of the CTI module. Although that did require starting a perf session, which might complicated the test.
Add a helper arm_trbe_disable_cpu() to disable TRBE precpu irq and reset per TRBE. Simply call arm_trbe_remove_coresight_cpu() directly without useing the smp_call_function_single(), which is the same as registering the TRBE coresight device.
Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver") Signed-off-by: Junhao He hejunhao3@huawei.com Link: https://lore.kernel.org/r/20230814093813.19152-2-hejunhao3@huawei.com [ Remove duplicate cpumask checks during removal ] Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com
drivers/hwtracing/coresight/coresight-trbe.c | 33 +++++++++++--------- 1 file changed, 18 insertions(+), 15 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c index 7720619909d6..025f70adee47 100644 --- a/drivers/hwtracing/coresight/coresight-trbe.c +++ b/drivers/hwtracing/coresight/coresight-trbe.c @@ -1225,6 +1225,17 @@ static void arm_trbe_enable_cpu(void *info) enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE); } +static void arm_trbe_disable_cpu(void *info) +{ + struct trbe_drvdata *drvdata = info; + struct trbe_cpudata *cpudata = this_cpu_ptr(drvdata->cpudata);
+ disable_percpu_irq(drvdata->irq); + trbe_reset_local(cpudata); + cpudata->drvdata = NULL; +}
static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cpu) { struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu); @@ -1326,18 +1337,12 @@ static void arm_trbe_probe_cpu(void *info) cpumask_clear_cpu(cpu, &drvdata->supported_cpus); } -static void arm_trbe_remove_coresight_cpu(void *info) +static void arm_trbe_remove_coresight_cpu(struct trbe_drvdata *drvdata, int cpu) { - int cpu = smp_processor_id(); - struct trbe_drvdata *drvdata = info; - struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu); struct coresight_device *trbe_csdev = coresight_get_percpu_sink(cpu); - disable_percpu_irq(drvdata->irq); - trbe_reset_local(cpudata); if (trbe_csdev) { coresight_unregister(trbe_csdev); - cpudata->drvdata = NULL; coresight_set_percpu_sink(cpu, NULL); } } @@ -1366,8 +1371,10 @@ static int arm_trbe_remove_coresight(struct trbe_drvdata *drvdata) { int cpu; - for_each_cpu(cpu, &drvdata->supported_cpus) - smp_call_function_single(cpu, arm_trbe_remove_coresight_cpu, drvdata, 1); + for_each_cpu(cpu, &drvdata->supported_cpus) { + smp_call_function_single(cpu, arm_trbe_disable_cpu, drvdata, 1); + arm_trbe_remove_coresight_cpu(drvdata, cpu); + } free_percpu(drvdata->cpudata); return 0; } @@ -1406,12 +1413,8 @@ static int arm_trbe_cpu_teardown(unsigned int cpu, struct hlist_node *node) { struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node); - if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) { - struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
- disable_percpu_irq(drvdata->irq); - trbe_reset_local(cpudata); - } + if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) + arm_trbe_disable_cpu(drvdata);
This code hunk seems unrelated to the context here other than just finding another use case for arm_trbe_disable_cpu(). The problem is - arm_trbe_disable_cpu() resets cpudata->drvdata which might not get re-initialized back in arm_trbe_cpu_startup(), as there will still be a per cpu sink associated as confirmed with coresight_get_percpu_sink(). I guess it might be better to drop this change and just keep everything limited to SMP IPI callback reworking in arm_trbe_remove_coresight().
OK, will fix it. The change is just to simplify the code of cpu_teardown. Maybe we can consider whether we need to set "cpudata->drvdata = NULL" in arm_trbe_disable_cpu()? If it's not necessary, This can be kept. Then drop the release cpudata->drvdata from arm_trbe_disable_cpu().
Best regards, Junhao.
return 0; }
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