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Fri, 21 May 2021 16:37:43 +0000 Subject: Re: [PATCH] hungtask: add filter kthread/check comm To: chenguanyou , linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, keescook@chromium.org, mhocko@suse.com, lukas.bulwahn@gmail.com, vbabka@suse.cz, gpiccoli@canonical.com, chenguanyou References: <20210521132503.19740-1-chenguanyou@xiaomi.com> From: Randy Dunlap Message-ID: <2421c8ea-de79-90df-08b6-51f15e859657@infradead.org> Date: Fri, 21 May 2021 09:37:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210521132503.19740-1-chenguanyou@xiaomi.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/21/21 6:25 AM, chenguanyou wrote: > Some kernel threads are always in D state, when we enable hung_task, > it will misjudge, we should skip these to narrow the scope. > > exp mtk mobilephone: > root 420 420 2 0 0 kwdt_thread 0 D wdtk-0 > root 421 421 2 0 0 kwdt_thread 0 D wdtk-1 > root 422 422 2 0 0 kwdt_thread 0 D wdtk-2 > root 423 423 2 0 0 kwdt_thread 0 D wdtk-3 > root 424 424 2 0 0 kwdt_thread 0 D wdtk-4 > root 425 425 2 0 0 kwdt_thread 0 D wdtk-5 > root 426 426 2 0 0 kwdt_thread 0 D wdtk-6 > root 427 427 2 0 0 kwdt_thread 0 D wdtk-7 > root 435 435 2 0 0 mtk_lpm_monitor_thread 0 D LPM-0 > root 436 436 2 0 0 mtk_lpm_monitor_thread 0 D LPM-1 > root 437 437 2 0 0 mtk_lpm_monitor_thread 0 D LPM-2 > root 438 438 2 0 0 mtk_lpm_monitor_thread 0 D LPM-3 > root 439 439 2 0 0 mtk_lpm_monitor_thread 0 D LPM-4 > root 440 440 2 0 0 mtk_lpm_monitor_thread 0 D LPM-5 > root 441 441 2 0 0 mtk_lpm_monitor_thread 0 D LPM-6 > root 442 442 2 0 0 mtk_lpm_monitor_thread 0 D LPM-7 > > Signed-off-by: chenguanyou > --- > include/linux/sched/sysctl.h | 4 ++++ > kernel/hung_task.c | 17 +++++++++++++++++ > kernel/sysctl.c | 16 ++++++++++++++++ > lib/Kconfig.debug | 24 ++++++++++++++++++++++++ > 4 files changed, 61 insertions(+) > > diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h > index 3c31ba88aca5..e8a9a28215bf 100644 > --- a/include/linux/sched/sysctl.h > +++ b/include/linux/sched/sysctl.h > @@ -14,11 +14,15 @@ extern unsigned int sysctl_hung_task_all_cpu_backtrace; > #define sysctl_hung_task_all_cpu_backtrace 0 > #endif /* CONFIG_SMP */ > > +#define TASK_COMM_LEN 16 > + > extern int sysctl_hung_task_check_count; > extern unsigned int sysctl_hung_task_panic; > extern unsigned long sysctl_hung_task_timeout_secs; > extern unsigned long sysctl_hung_task_check_interval_secs; > extern int sysctl_hung_task_warnings; > +extern unsigned int sysctl_hung_task_filter_kthread; > +extern char sysctl_hung_task_check_comm[TASK_COMM_LEN]; > int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, > void *buffer, size_t *lenp, loff_t *ppos); > #else > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index 396ebaebea3f..e018563d4882 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -23,6 +23,7 @@ > #include > > #include > +#include > > /* > * The number of tasks checked: > @@ -48,6 +49,16 @@ unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_ > */ > unsigned long __read_mostly sysctl_hung_task_check_interval_secs; > > +/* > + * Non zero means no checking kthread Non-zero (also mentioned in v1 review, whereas this is v2, I guess, although it doesn't say that it is v2, but it should say that.) > + */ > +unsigned int __read_mostly sysctl_hung_task_filter_kthread = CONFIG_DEFAULT_HUNG_TASK_FILTER_KTHREAD; > + > +/* > + * Only one > + */ > +char __read_mostly sysctl_hung_task_check_comm[TASK_COMM_LEN] = CONFIG_DEFAULT_HUNG_TASK_CHECK_COMM; > + > int __read_mostly sysctl_hung_task_warnings = 10; > > static int __read_mostly did_panic; > @@ -88,6 +99,12 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > { > unsigned long switch_count = t->nvcsw + t->nivcsw; > > + if (unlikely(strlen(sysctl_hung_task_check_comm) && !strstr(t->comm, sysctl_hung_task_check_comm))) > + return; > + > + if (unlikely(sysctl_hung_task_filter_kthread && t->flags & PF_KTHREAD)) > + return; > + > /* > * Ensure the task is not frozen. > * Also, skip vfork and any other user process that freezer should skip. > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 62fbd09b5dc1..1daede87c88d 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -2519,6 +2519,22 @@ static struct ctl_table kern_table[] = { > .proc_handler = proc_dointvec_minmax, > .extra1 = &neg_one, > }, > + { > + .procname = "hung_task_filter_kthread", > + .data = &sysctl_hung_task_filter_kthread, > + .maxlen = sizeof(int), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = SYSCTL_ZERO, > + .extra2 = SYSCTL_ONE, > + }, > + { > + .procname = "hung_task_check_comm", > + .data = &sysctl_hung_task_check_comm, > + .maxlen = TASK_COMM_LEN, > + .mode = 0644, > + .proc_handler = proc_dostring, > + }, (copy-paste from v1 review:) These new sysctls should be documented in Documentation/admin-guide/sysctl/kernel.rst. > #endif > #ifdef CONFIG_RT_MUTEXES > { > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 2c7f46b366f1..6eab8cf0c37f 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1101,6 +1101,30 @@ config DEFAULT_HUNG_TASK_TIMEOUT > A timeout of 0 disables the check. The default is two minutes. > Keeping the default should be fine in most cases. > > +config DEFAULT_HUNG_TASK_FILTER_KTHREAD > + int "Default filter kthread for hung task" > + depends on DETECT_HUNG_TASK > + range 0 1 > + default 0 > + help > + This option controls filter kthread used to determine when (again:) uses > + a kernel task has become "state=TASK_UNINTERRUPTIBLE" and should be skip. (again:) skipped. > + > + It can be adjusted at runtime via the kernel.hung_task_filter_kthread > + sysctl or by writing a value to > + /proc/sys/kernel/hung_task_filter_kthread. > + > + A filter of 1 disables the check (again:) check. > + > +config DEFAULT_HUNG_TASK_CHECK_COMM > + string "Default check only one comm" > + depends on DETECT_HUNG_TASK > + default "" > + help > + It can be adjusted at runtime via the kernel.hung_task_check_comm > + sysctl or by writing a value to > + /proc/sys/kernel/hung_task_check_comm. > + (again:) That help text doesn't tell how the Kconfig symbol is used. > config BOOTPARAM_HUNG_TASK_PANIC > bool "Panic (Reboot) On Hung Tasks" > depends on DETECT_HUNG_TASK > -- ~Randy