From: David Vernet <void@manifault.com> mainline inclusion from mainline-v6.12-rc1 commit 1538e33995eaf3f315cbb5506019b9f913ed8555 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- It would be useful to see what the sched_ext scheduler state is, and what scheduler is running, when we're dumping a task's stack. This patch therefore adds a new print_scx_info() function that's called in the same context as print_worker_info() and print_stop_info(). An example dump follows. BUG: kernel NULL pointer dereference, address: 0000000000000999 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP CPU: 13 PID: 2047 Comm: insmod Tainted: G O 6.6.0-work-10323-gb58d4cae8e99-dirty #34 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 2/2/2022 Sched_ext: qmap (enabled+all), task: runnable_at=-17ms RIP: 0010:init_module+0x9/0x1000 [test_module] ... v3: - scx_ops_enable_state_str[] definition moved to an earlier patch as it's now used by core implementation. - Convert jiffy delta to msecs using jiffies_to_msecs() instead of multiplying by (HZ / MSEC_PER_SEC). The conversion is implemented in jiffies_delta_msecs(). v2: - We are now using scx_ops_enable_state_str[] outside CONFIG_SCHED_DEBUG. Move it outside of CONFIG_SCHED_DEBUG and to the top. This was reported by Changwoo and Andrea. Signed-off-by: David Vernet <void@manifault.com> Reported-by: Changwoo Min <changwoo@igalia.com> Reported-by: Andrea Righi <andrea.righi@canonical.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- include/linux/sched/ext.h | 2 ++ kernel/sched/core.c | 1 + kernel/sched/ext.c | 53 +++++++++++++++++++++++++++++++++++++++ lib/dump_stack.c | 1 + 4 files changed, 57 insertions(+) diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h index ea7c501ac819..85fb5dc725ef 100644 --- a/include/linux/sched/ext.h +++ b/include/linux/sched/ext.h @@ -155,10 +155,12 @@ struct sched_ext_entity { }; void sched_ext_free(struct task_struct *p); +void print_scx_info(const char *log_lvl, struct task_struct *p); #else /* !CONFIG_SCHED_CLASS_EXT */ static inline void sched_ext_free(struct task_struct *p) {} +static inline void print_scx_info(const char *log_lvl, struct task_struct *p) {} #endif /* CONFIG_SCHED_CLASS_EXT */ #endif /* _LINUX_SCHED_EXT_H */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7722032cd236..da5b6769d2a1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7489,6 +7489,7 @@ void sched_show_task(struct task_struct *p) print_worker_info(KERN_INFO, p); print_stop_info(KERN_INFO, p); + print_scx_info(KERN_INFO, p); show_stack(p, NULL, KERN_INFO); put_task_stack(p); } diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index e4eea4c56513..bced809e3e8c 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -590,6 +590,14 @@ static __printf(3, 4) void scx_ops_exit_kind(enum scx_exit_kind kind, #define SCX_HAS_OP(op) static_branch_likely(&scx_has_op[SCX_OP_IDX(op)]) +static long jiffies_delta_msecs(unsigned long at, unsigned long now) +{ + if (time_after(at, now)) + return jiffies_to_msecs(at - now); + else + return -(long)jiffies_to_msecs(now - at); +} + /* if the highest set bit is N, return a mask with bits [N+1, 31] set */ static u32 higher_bits(u32 flags) { @@ -3720,6 +3728,51 @@ static const struct sysrq_key_op sysrq_sched_ext_reset_op = { .enable_mask = SYSRQ_ENABLE_RTNICE, }; +/** + * print_scx_info - print out sched_ext scheduler state + * @log_lvl: the log level to use when printing + * @p: target task + * + * If a sched_ext scheduler is enabled, print the name and state of the + * scheduler. If @p is on sched_ext, print further information about the task. + * + * This function can be safely called on any task as long as the task_struct + * itself is accessible. While safe, this function isn't synchronized and may + * print out mixups or garbages of limited length. + */ +void print_scx_info(const char *log_lvl, struct task_struct *p) +{ + enum scx_ops_enable_state state = scx_ops_enable_state(); + const char *all = READ_ONCE(scx_switching_all) ? "+all" : ""; + char runnable_at_buf[22] = "?"; + struct sched_class *class; + unsigned long runnable_at; + + if (state == SCX_OPS_DISABLED) + return; + + /* + * Carefully check if the task was running on sched_ext, and then + * carefully copy the time it's been runnable, and its state. + */ + if (copy_from_kernel_nofault(&class, &p->sched_class, sizeof(class)) || + class != &ext_sched_class) { + printk("%sSched_ext: %s (%s%s)", log_lvl, scx_ops.name, + scx_ops_enable_state_str[state], all); + return; + } + + if (!copy_from_kernel_nofault(&runnable_at, &p->scx.runnable_at, + sizeof(runnable_at))) + scnprintf(runnable_at_buf, sizeof(runnable_at_buf), "%+ldms", + jiffies_delta_msecs(runnable_at, jiffies)); + + /* print everything onto one line to conserve console space */ + printk("%sSched_ext: %s (%s%s), task: runnable_at=%s", + log_lvl, scx_ops.name, scx_ops_enable_state_str[state], all, + runnable_at_buf); +} + void __init init_sched_ext_class(void) { s32 cpu, v; diff --git a/lib/dump_stack.c b/lib/dump_stack.c index 83471e81501a..6e667c445539 100644 --- a/lib/dump_stack.c +++ b/lib/dump_stack.c @@ -68,6 +68,7 @@ void dump_stack_print_info(const char *log_lvl) print_worker_info(log_lvl, current); print_stop_info(log_lvl, current); + print_scx_info(log_lvl, current); } /** -- 2.34.1