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Date: Fri, 28 Jan 2022 15:48:05 +0100 From: Oliver Hartkopp <socketcan@...tkopp.net> To: Marc Kleine-Budde <mkl@...gutronix.de>, "Ziyang Xuan (William)" <william.xuanziyang@...wei.com> Cc: davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net] can: isotp: isotp_rcv_cf(): fix so->rx race problem Hello Marc, hello William, On 28.01.22 09:46, Marc Kleine-Budde wrote: > On 28.01.2022 09:32:40, Oliver Hartkopp wrote: >> >> >> On 28.01.22 09:07, Marc Kleine-Budde wrote: >>> On 28.01.2022 08:56:19, Oliver Hartkopp wrote: >>>> I've seen the frame processing sometimes freezes for one second when >>>> stressing the isotp_rcv() from multiple sources. This finally freezes >>>> the entire softirq which is either not good and not needed as we only >>>> need to fix this race for stress tests - and not for real world usage >>>> that does not create this case. >>> >>> Hmmm, this doesn't sound good. Can you test with LOCKDEP enabled? >> # >> # Lock Debugging (spinlocks, mutexes, etc...) >> # >> CONFIG_LOCK_DEBUGGING_SUPPORT=y >> # CONFIG_PROVE_LOCKING is not set > CONFIG_PROVE_LOCKING=y Now enabled even more locking (seen relevant kernel config at the end). It turns out that there is no visible difference when using spin_lock() or spin_trylock(). I only got some of these kernel log entries Jan 28 11:13:14 silver kernel: [ 2396.323211] perf: interrupt took too long (2549 > 2500), lowering kernel.perf_event_max_sample_rate to 78250 Jan 28 11:25:49 silver kernel: [ 3151.172773] perf: interrupt took too long (3188 > 3186), lowering kernel.perf_event_max_sample_rate to 62500 Jan 28 11:45:24 silver kernel: [ 4325.583328] perf: interrupt took too long (4009 > 3985), lowering kernel.perf_event_max_sample_rate to 49750 Jan 28 12:15:46 silver kernel: [ 6148.238246] perf: interrupt took too long (5021 > 5011), lowering kernel.perf_event_max_sample_rate to 39750 Jan 28 13:01:45 silver kernel: [ 8907.303715] perf: interrupt took too long (6285 > 6276), lowering kernel.perf_event_max_sample_rate to 31750 But I get these sporadically anyway. No other LOCKDEP splat. At least the issue reported by William should be fixed now - but I'm still unclear whether spin_lock() or spin_trylock() is the best approach here in the NET_RX softirq?!? Best regards, Oliver $ grep LOCK .config | grep -v BLOCK | grep -v CLOCK CONFIG_LOCKDEP_SUPPORT=y # CONFIG_PM_WAKELOCKS is not set CONFIG_HAVE_HARDLOCKUP_DETECTOR_PERF=y # CONFIG_LOCK_EVENT_COUNTS is not set CONFIG_UNINLINE_SPIN_UNLOCK=y CONFIG_LOCK_SPIN_ON_OWNER=y CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y CONFIG_QUEUED_SPINLOCKS=y CONFIG_ARCH_USE_QUEUED_RWLOCKS=y CONFIG_QUEUED_RWLOCKS=y CONFIG_SPLIT_PTLOCK_CPUS=4 CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK=y CONFIG_PCI_LOCKLESS_CONFIG=y # CONFIG_DRM_DEBUG_MODESET_LOCK is not set CONFIG_HWSPINLOCK=y CONFIG_I8253_LOCK=y CONFIG_FILE_LOCKING=y # CONFIG_SECURITY_LOCKDOWN_LSM is not set # CONFIG_SECURITY_LANDLOCK is not set # CONFIG_CRYPTO_DEV_PADLOCK is not set CONFIG_ARCH_USE_CMPXCHG_LOCKREF=y CONFIG_LOCKUP_DETECTOR=y CONFIG_SOFTLOCKUP_DETECTOR=y # CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE=0 CONFIG_HARDLOCKUP_DETECTOR_PERF=y CONFIG_HARDLOCKUP_CHECK_TIMESTAMP=y CONFIG_HARDLOCKUP_DETECTOR=y # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=0 # CONFIG_TEST_LOCKUP is not set CONFIG_LOCK_DEBUGGING_SUPPORT=y CONFIG_PROVE_LOCKING=y CONFIG_PROVE_RAW_LOCK_NESTING=y # CONFIG_LOCK_STAT is not set CONFIG_DEBUG_SPINLOCK=y CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_LOCKDEP=y CONFIG_LOCKDEP_BITS=15 CONFIG_LOCKDEP_CHAINS_BITS=16 CONFIG_LOCKDEP_STACK_TRACE_BITS=19 CONFIG_LOCKDEP_STACK_TRACE_HASH_BITS=14 CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12 CONFIG_DEBUG_LOCKDEP=y # CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set # CONFIG_LOCK_TORTURE_TEST is not set # CONFIG_CSD_LOCK_WAIT_DEBUG is not set
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