diff options
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 5 | ||||
| -rw-r--r-- | kernel/hung_task.c | 49 |
2 files changed, 44 insertions, 10 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index b6328cd0f43e..31fbc8c9184c 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -459,8 +459,9 @@ hung_task_warnings ================== The maximum number of warnings to report. During a check interval -if a hung task is detected, this value is decreased by 1. -When this value reaches 0, no more warnings will be reported. +if a hung task is detected, the internal warning budget is decreased by 1. +When this budget reaches 0, no more detailed warnings will be reported. The +warning budget is reset to the configured limit when no hung task is found. This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -1: report an infinite number of warnings. diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 6fcc94ce4ca9..a5043188456d 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -57,8 +57,20 @@ unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_ */ static unsigned long __read_mostly sysctl_hung_task_check_interval_secs; +/* + * Limit the number of printed hung tasks to prevent printing + * the same or similar backtraces repeatedly. + */ static int __read_mostly sysctl_hung_task_warnings = 10; +/* + * The number of hung tasks which still can be reported. + * The budget gets restored to the original limit when + * the previous stall is resolved. + */ +static int hung_task_warnings_budget = 10; +static atomic_t reset_hung_task_warnings = ATOMIC_INIT(0); + static int __read_mostly did_panic; static bool hung_task_call_panic; @@ -245,11 +257,11 @@ static void hung_task_info(struct task_struct *t, unsigned long timeout, /* * The given task did not get scheduled for more than * CONFIG_DEFAULT_HUNG_TASK_TIMEOUT. Therefore, complain - * accordingly + * accordingly with full details if the budget is not exhausted. */ - if (sysctl_hung_task_warnings || hung_task_call_panic) { - if (sysctl_hung_task_warnings > 0) - sysctl_hung_task_warnings--; + if (hung_task_warnings_budget || hung_task_call_panic) { + if (hung_task_warnings_budget > 0) + hung_task_warnings_budget--; pr_err("INFO: task %s:%d blocked%s for more than %ld seconds.\n", t->comm, t->pid, t->in_iowait ? " in I/O wait" : "", (jiffies - t->last_switch_time) / HZ); @@ -264,7 +276,7 @@ static void hung_task_info(struct task_struct *t, unsigned long timeout, sched_show_task(t); debug_show_blocker(t, timeout); - if (!sysctl_hung_task_warnings) + if (!hung_task_warnings_budget) pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n"); } @@ -304,7 +316,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) unsigned long last_break = jiffies; struct task_struct *g, *t; unsigned long this_round_count; - int need_warning = sysctl_hung_task_warnings; + int need_warning; unsigned long si_mask = hung_task_si_mask; /* @@ -314,6 +326,11 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) if (test_taint(TAINT_DIE) || did_panic) return; + if (atomic_xchg_acquire(&reset_hung_task_warnings, 0)) + hung_task_warnings_budget = + READ_ONCE(sysctl_hung_task_warnings); + need_warning = hung_task_warnings_budget; + this_round_count = 0; rcu_read_lock(); for_each_process_thread(g, t) { @@ -340,8 +357,11 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) unlock: rcu_read_unlock(); - if (!this_round_count) + if (!this_round_count) { + hung_task_warnings_budget = + READ_ONCE(sysctl_hung_task_warnings); return; + } if (need_warning || hung_task_call_panic) { si_mask |= SYS_INFO_LOCKS; @@ -425,6 +445,19 @@ static int proc_dohung_task_timeout_secs(const struct ctl_table *table, int writ return ret; } +static int proc_dohung_task_warnings(const struct ctl_table *table, int write, + void *buffer, + size_t *lenp, loff_t *ppos) +{ + int ret; + + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (!ret && write) + atomic_set_release(&reset_hung_task_warnings, 1); + + return ret; +} + /* * This is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs * and hung_task_check_interval_secs @@ -480,7 +513,7 @@ static const struct ctl_table hung_task_sysctls[] = { .data = &sysctl_hung_task_warnings, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_dohung_task_warnings, .extra1 = SYSCTL_NEG_ONE, }, { |