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60c27fb59f
Add ops.cpu_online/offline() which are invoked when CPUs come online and
offline respectively. As the enqueue path already automatically bypasses
tasks to the local dsq on a deactivated CPU, BPF schedulers are guaranteed
to see tasks only on CPUs which are between online() and offline().
If the BPF scheduler doesn't implement ops.cpu_online/offline(), the
scheduler is automatically exited with SCX_ECODE_RESTART |
SCX_ECODE_RSN_HOTPLUG. Userspace can implement CPU hotpplug support
trivially by simply reinitializing and reloading the scheduler.
scx_qmap is updated to print out online CPUs on hotplug events. Other
schedulers are updated to restart based on ecode.
v3: - The previous implementation added @reason to
sched_class.rq_on/offline() to distinguish between CPU hotplug events
and topology updates. This was buggy and fragile as the methods are
skipped if the current state equals the target state. Instead, add
scx_rq_[de]activate() which are directly called from
sched_cpu_de/activate(). This also allows ops.cpu_on/offline() to
sleep which can be useful.
- ops.dispatch() could be called on a CPU that the BPF scheduler was
told to be offline. The dispatch patch is updated to bypass in such
cases.
v2: - To accommodate lock ordering change between scx_cgroup_rwsem and
cpus_read_lock(), CPU hotplug operations are put into its own SCX_OPI
block and enabled eariler during scx_ope_enable() so that
cpus_read_lock() can be dropped before acquiring scx_cgroup_rwsem.
- Auto exit with ECODE added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
112 lines
3.5 KiB
C
112 lines
3.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Define struct user_exit_info which is shared between BPF and userspace parts
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* to communicate exit status and other information.
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*
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* Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
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* Copyright (c) 2022 Tejun Heo <tj@kernel.org>
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* Copyright (c) 2022 David Vernet <dvernet@meta.com>
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*/
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#ifndef __USER_EXIT_INFO_H
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#define __USER_EXIT_INFO_H
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enum uei_sizes {
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UEI_REASON_LEN = 128,
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UEI_MSG_LEN = 1024,
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UEI_DUMP_DFL_LEN = 32768,
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};
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struct user_exit_info {
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int kind;
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s64 exit_code;
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char reason[UEI_REASON_LEN];
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char msg[UEI_MSG_LEN];
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};
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#ifdef __bpf__
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#include "vmlinux.h"
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#include <bpf/bpf_core_read.h>
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#define UEI_DEFINE(__name) \
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char RESIZABLE_ARRAY(data, __name##_dump); \
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const volatile u32 __name##_dump_len; \
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struct user_exit_info __name SEC(".data")
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#define UEI_RECORD(__uei_name, __ei) ({ \
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bpf_probe_read_kernel_str(__uei_name.reason, \
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sizeof(__uei_name.reason), (__ei)->reason); \
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bpf_probe_read_kernel_str(__uei_name.msg, \
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sizeof(__uei_name.msg), (__ei)->msg); \
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bpf_probe_read_kernel_str(__uei_name##_dump, \
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__uei_name##_dump_len, (__ei)->dump); \
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if (bpf_core_field_exists((__ei)->exit_code)) \
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__uei_name.exit_code = (__ei)->exit_code; \
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/* use __sync to force memory barrier */ \
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__sync_val_compare_and_swap(&__uei_name.kind, __uei_name.kind, \
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(__ei)->kind); \
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})
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#else /* !__bpf__ */
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#include <stdio.h>
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#include <stdbool.h>
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/* no need to call the following explicitly if SCX_OPS_LOAD() is used */
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#define UEI_SET_SIZE(__skel, __ops_name, __uei_name) ({ \
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u32 __len = (__skel)->struct_ops.__ops_name->exit_dump_len ?: UEI_DUMP_DFL_LEN; \
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(__skel)->rodata->__uei_name##_dump_len = __len; \
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RESIZE_ARRAY((__skel), data, __uei_name##_dump, __len); \
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})
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#define UEI_EXITED(__skel, __uei_name) ({ \
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/* use __sync to force memory barrier */ \
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__sync_val_compare_and_swap(&(__skel)->data->__uei_name.kind, -1, -1); \
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})
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#define UEI_REPORT(__skel, __uei_name) ({ \
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struct user_exit_info *__uei = &(__skel)->data->__uei_name; \
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char *__uei_dump = (__skel)->data_##__uei_name##_dump->__uei_name##_dump; \
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if (__uei_dump[0] != '\0') { \
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fputs("\nDEBUG DUMP\n", stderr); \
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fputs("================================================================================\n\n", stderr); \
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fputs(__uei_dump, stderr); \
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fputs("\n================================================================================\n\n", stderr); \
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} \
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fprintf(stderr, "EXIT: %s", __uei->reason); \
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if (__uei->msg[0] != '\0') \
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fprintf(stderr, " (%s)", __uei->msg); \
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fputs("\n", stderr); \
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__uei->exit_code; \
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})
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/*
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* We can't import vmlinux.h while compiling user C code. Let's duplicate
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* scx_exit_code definition.
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*/
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enum scx_exit_code {
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/* Reasons */
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SCX_ECODE_RSN_HOTPLUG = 1LLU << 32,
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/* Actions */
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SCX_ECODE_ACT_RESTART = 1LLU << 48,
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};
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enum uei_ecode_mask {
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UEI_ECODE_USER_MASK = ((1LLU << 32) - 1),
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UEI_ECODE_SYS_RSN_MASK = ((1LLU << 16) - 1) << 32,
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UEI_ECODE_SYS_ACT_MASK = ((1LLU << 16) - 1) << 48,
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};
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/*
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* These macro interpret the ecode returned from UEI_REPORT().
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*/
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#define UEI_ECODE_USER(__ecode) ((__ecode) & UEI_ECODE_USER_MASK)
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#define UEI_ECODE_SYS_RSN(__ecode) ((__ecode) & UEI_ECODE_SYS_RSN_MASK)
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#define UEI_ECODE_SYS_ACT(__ecode) ((__ecode) & UEI_ECODE_SYS_ACT_MASK)
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#define UEI_ECODE_RESTART(__ecode) (UEI_ECODE_SYS_ACT((__ecode)) == SCX_ECODE_ACT_RESTART)
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#endif /* __bpf__ */
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#endif /* __USER_EXIT_INFO_H */
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