- 12 Mar, 2010 40 commits
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining arch_has_single_step in <asm/ptrace.h> and implementing the user_enable_single_step and user_disable_single_step functions, which also causes the breakpoint information to be cleared on fork, which could be considered a bug fix. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. XXX: I'm not sure arch_has_single_step() is placed in the exactly correct location, please verify in which of the ptrace headers it should really be. Signed-off-by:
Christoph Hellwig <hch@lst.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT and PTRACE_KILL. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. Signed-off-by:
Ralf Baechle <ralf@linux-mips.org> Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT and PTRACE_KILL. This also makes PTRACE_SINGLESTEP return -EIO while it previously succeeded despite not actually causing any kind of single stepping. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. Signed-off-by:
Michal Simek <monstr@monstr.eu> Cc: John Williams <john.williams@petalogix.com> Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. m68knommu already defines the nessecary user_enable_single_step and user_disable_single_step functions for this. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. Signed-off-by:
Greg Ungerer <gerg@uclinux.org> Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining arch_has_single_step in <asm/ptrace.h> and implementing the user_enable_single_step and user_disable_single_step functions, which also causes the breakpoint information to be cleared on fork, which could be considered a bug fix. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining arch_has_single_step in <asm/ptrace.h> and implementing the user_enable_single_step and user_disable_single_step functions, which also causes the breakpoint information to be cleared on fork, which could be considered a bug fix. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't which is consistent with all architectures using the modern ptrace code. Currently avr32 doesn't implement any code to disable single stepping when one of the non-syscall requests is called which seems wrong, but I've left it as-is for now. Signed-off-by:
Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining arch_has_single_step in <asm/ptrace.h> and implementing the user_enable_single_step and user_disable_single_step functions, which also causes the breakpoint information to be cleared on fork, which could be considered a bug fix. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't and the single stepping disable only happens if the tracee process isn't a zombie yet, which is consistent with all architectures using the modern ptrace code. Signed-off-by:
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Christoph Hellwig authored
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT, PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining arch_has_single_step in <asm/ptrace.h> and implementing the user_enable_single_step and user_disable_single_step functions, which also causes the breakpoint information to be cleared on fork, which could be considered a bug fix. Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL which it previously wasn't, which is consistent with all architectures using the modern ptrace code. Signed-off-by:
Matt Turner <mattst88@gmail.com> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Richard Henderson <rth@twiddle.net> Signed-off-by:
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Christoph Hellwig authored
While in theory user_enable_single_step/user_disable_single_step/ user_enable_blockstep could also be provided as an inline or macro there's no good reason to do so, and having the prototype in one places keeps code size and confusion down. Roland said: The original thought there was that user_enable_single_step() et al might well be only an instruction or three on a sane machine (as if we have any of those!), and since there is only one call site inlining would be beneficial. But I agree that there is no strong reason to care about inlining it. As to the arch changes, there is only one thought I'd add to the record. It was always my thinking that for an arch where PTRACE_SINGLESTEP does text-modifying breakpoint insertion, user_enable_single_step() should not be provided. That is, arch_has_single_step()=>true means that there is an arch facility with "pure" semantics that does not have any unexpected side effects. Inserting a breakpoint might do very unexpected strange things in multi-threaded situations. Aside from that, it is a peculiar side effect that user_{enable,disable}_single_step() should cause COW de-sharing of text pages and so forth. For PTRACE_SINGLESTEP, all these peculiarities are the status quo ante for that arch, so having arch_ptrace() itself do those is one thing. But for building other things in the future, it is nicer to have a uniform "pure" semantics that arch-independent code can expect. OTOH, all such arch issues are really up to the arch maintainer. As of today, there is nothing but ptrace using user_enable_single_step() et al so it's a distinction without a practical difference. If/when there are other facilities that use user_enable_single_step() and might care, the affected arch's can revisit the question when someone cares about the quality of the arch support for said new facility. Signed-off-by:David Howells <dhowells@redhat.com> Signed-off-by:
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Christoph Hellwig authored
Use ptrace_request() in the three remaining architectures that didn't use it (m68knommu, h8300, microblaze). This means: - ptrace_request now handles PTRACE_{PEEK,POKE}{TEXT,DATA} and PTRACE_DETATCH calls that were previously called directly, or in case of h8300 even open coded. - adds new support for PTRACE_SETOPTIONS/PTRACE_GETEVENTMSG/ PTRACE_GETSIGINFO/PTRACE_SETSIGINFO Signed-off-by:Roland McGrath <roland@redhat.com> Signed-off-by:
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Miao Xie authored
we can't declarate two variable at the same scope by NODEMASK_ALLOC(). This patch fixes it. Signed-off-by:
Miao Xie <miaox@cn.fujitsu.com> Cc: David Rientjes <rientjes@google.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Paul Menage <menage@google.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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KAMEZAWA Hiroyuki authored
Nishimura-san have been working for memcg very good. His review and tests give us much improvements and account migraiton which he is now challenging is really important. He is a stakeholder. Signed-off-by:
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by:
Pavel Emelyanov <xemul@openvz.org> Signed-off-by:
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KAMEZAWA Hiroyuki authored
In current page-fault code, handle_mm_fault() -> ... -> mem_cgroup_charge() -> map page or handle error. -> check return code. If page fault's return code is VM_FAULT_OOM, page_fault_out_of_memory() is called. But if it's caused by memcg, OOM should have been already invoked. Then, I added a patch: a636b327. That patch records last_oom_jiffies for memcg's sub-hierarchy and prevents page_fault_out_of_memory from being invoked in near future. But Nishimura-san reported that check by jiffies is not enough when the system is terribly heavy. This patch changes memcg's oom logic as. * If memcg causes OOM-kill, continue to retry. * remove jiffies check which is used now. * add memcg-oom-lock which works like perzone oom lock. * If current is killed(as a process), bypass charge. Something more sophisticated can be added but this pactch does fundamental things. TODO: - add oom notifier - add permemcg disable-oom-kill flag and freezer at oom. - more chances for wake up oom waiter (when changing memory limit etc..) Reviewed-by:
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Tested-by:
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Kirill A. Shutemov authored
Signed-off-by:
Kirill A. Shutemov <kirill@shutemov.name> Reviewed-by:
Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by:
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Kirill A. Shutemov authored
Decription of sanity check for memory thresholds. Signed-off-by:
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Kirill A. Shutemov authored
An example of cgroup notification API usage. Signed-off-by:
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Kirill A. Shutemov authored
Events should be removed after rmdir of cgroup directory, but before destroying subsystem state objects. Let's take reference to cgroup directory dentry to do that. Signed-off-by:
KAMEZAWA Hiroyuki <kamezawa.hioryu@jp.fujitsu.com> Cc: Paul Menage <menage@google.com> Acked-by:
Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Dan Malek <dan@embeddedalley.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by:
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Kirill A. Shutemov authored
Notify userspace about cgroup removing only after rmdir of cgroup directory to avoid race between userspace and kernelspace. eventfd are used to notify about two types of event: - control file-specific, like crossing memory threshold; - cgroup removing. To understand what really happen, userspace can check if the cgroup still exists. To avoid race beetween userspace and kernelspace we have to notify userspace about cgroup removing only after rmdir of cgroup directory. Signed-off-by:
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KAMEZAWA Hiroyuki authored
Presently, if panic_on_oom=2, the whole system panics even if the oom happend in some special situation (as cpuset, mempolicy....). Then, panic_on_oom=2 means painc_on_oom_always. Now, memcg doesn't check panic_on_oom flag. This patch adds a check. BTW, how it's useful ? kdump+panic_on_oom=2 is the last tool to investigate what happens in oom-ed system. When a task is killed, the sysytem recovers and there will be few hint to know what happnes. In mission critical system, oom should never happen. Then, panic_on_oom=2+kdump is useful to avoid next OOM by knowing precise information via snapshot. TODO: - For memcg, it's for isolate system's memory usage, oom-notiifer and freeze_at_oom (or rest_at_oom) should be implemented. Then, management daemon can do similar jobs (as kdump) or taking snapshot per cgroup. Signed-off-by:
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Daisuke Nishimura authored
Update memcg_test.txt to describe how to test the move-charge feature. Signed-off-by:
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KAMEZAWA Hiroyuki authored
Memcg has 2 eventcountes which counts "the same" event. Just usages are different from each other. This patch tries to reduce event counter. Now logic uses "only increment, no reset" counter and masks for each checks. Softlimit chesk was done per 1000 evetns. So, the similar check can be done by !(new_counter & 0x3ff). Threshold check was done per 100 events. So, the similar check can be done by (!new_counter & 0x7f) ALL event checks are done right after EVENT percpu counter is updated. Signed-off-by:
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KAMEZAWA Hiroyuki authored
Presently, move_task does "batched" precharge. Because res_counter or css's refcnt are not-scalable jobs for memcg, try_charge_().. tend to be done in batched manner if allowed. Now, softlimit and threshold check their event counter in try_charge, but the charge is not a per-page event. And event counter is not updated at charge(). Moreover, precharge doesn't pass "page" to try_charge() and softlimit tree will be never updated until uncharge() causes an event." So the best place to check the event counter is commit_charge(). This is per-page event by its nature. This patch move checks to there. Signed-off-by:
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KAMEZAWA Hiroyuki authored
When per-cpu counter for memcg was implemneted, dynamic percpu allocator was not very good. But now, we have good one and useful macros. This patch replaces memcg's private percpu counter implementation with generic dynamic percpu allocator. The benefits are - We can remove private implementation. - The counters will be NUMA-aware. (Current one is not...) - This patch makes sizeof struct mem_cgroup smaller. Then, struct mem_cgroup may be fit in page size on small config. - About basic performance aspects, see below. [Before] # size mm/memcontrol.o text data bss dec hex filename 24373 2528 4132 31033 7939 mm/memcontrol.o [page-fault-throuput test on 8cpu/SMP in root cgroup] # /root/bin/perf stat -a -e page-faults,cache-misses --repeat 5 ./multi-fault-fork 8 Performance counter stats for './multi-fault-fork 8' (5 runs): 45878618 page-faults ( +- 0.110% ) 602635826 cache-misses ( +- 0.105% ) 61.005373262 seconds time elapsed ( +- 0.004% ) Then cache-miss/page fault = 13.14 [After] #size mm/memcontrol.o text data bss dec hex filename 23913 2528 4132 30573 776d mm/memcontrol.o # /root/bin/perf stat -a -e page-faults,cache-misses --repeat 5 ./multi-fault-fork 8 Performance counter stats for './multi-fault-fork 8' (5 runs): 48179400 page-faults ( +- 0.271% ) 588628407 cache-misses ( +- 0.136% ) 61.004615021 seconds time elapsed ( +- 0.004% ) Then cache-miss/page fault = 12.22 Text size is reduced. This performance improvement is not big and will be invisible in real world applications. But this result shows this patch has some good effect even on (small) SMP. Here is a test program I used. 1. fork() processes on each cpus. 2. do page fault repeatedly on each process. 3. after 60secs, kill all childredn and exit. (3 is necessary for getting stable data, this is improvement from previous one.) #define _GNU_SOURCE #include <stdio.h> #include <sched.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <signal.h> #include <stdlib.h> /* * For avoiding contention in page table lock, FAULT area is * sparse. If FAULT_LENGTH is too large for your cpus, decrease it. */ #define FAULT_LENGTH (2 * 1024 * 1024) #define PAGE_SIZE 4096 #define MAXNUM (128) void alarm_handler(int sig) { } void *worker(int cpu, int ppid) { void *start, *end; char *c; cpu_set_t set; int i; CPU_ZERO(&set); CPU_SET(cpu, &set); sched_setaffinity(0, sizeof(set), &set); start = mmap(NULL, FAULT_LENGTH, PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); if (start == MAP_FAILED) { perror("mmap"); exit(1); } end = start + FAULT_LENGTH; pause(); //fprintf(stderr, "run%d", cpu); while (1) { for (c = (char*)start; (void *)c < end; c += PAGE_SIZE) *c = 0; madvise(start, FAULT_LENGTH, MADV_DONTNEED); } return NULL; } int main(int argc, char *argv[]) { int num, i, ret, pid, status; int pids[MAXNUM]; if (argc < 2) return 0; setpgid(0, 0); signal(SIGALRM, alarm_handler); num = atoi(argv[1]); pid = getpid(); for (i = 0; i < num; ++i) { ret = fork(); if (!ret) { worker(i, pid); exit(0); } pids[i] = ret; } sleep(1); kill(-pid, SIGALRM); sleep(60); for (i = 0; i < num; i++) kill(pids[i], SIGKILL); for (i = 0; i < num; i++) waitpid(pids[i], &status, 0); return 0; } Signed-off-by: -
Kirill A. Shutemov authored
s/mem_cgroup_print_mem_info/mem_cgroup_print_oom_info/ Signed-off-by:
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Kirill A. Shutemov authored
It allows to register multiple memory and memsw thresholds and gets notifications when it crosses. To register a threshold application need: - create an eventfd; - open memory.usage_in_bytes or memory.memsw.usage_in_bytes; - write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to cgroup.event_control. Application will be notified through eventfd when memory usage crosses threshold in any direction. It's applicable for root and non-root cgroup. It uses stats to track memory usage, simmilar to soft limits. It checks if we need to send event to userspace on every 100 page in/out. I guess it's good compromise between performance and accuracy of thresholds. [akpm@linux-foundation.org: coding-style fixes] [nishimura@mxp.nes.nec.co.jp: fix documentation merge issue] Signed-off-by:
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Kirill A. Shutemov authored
Instead of incrementing counter on each page in/out and comparing it with constant, we set counter to constant, decrement counter on each page in/out and compare it with zero. We want to make comparing as fast as possible. On many RISC systems (probably not only RISC) comparing with zero is more effective than comparing with a constant, since not every constant can be immediate operand for compare instruction. Also, I've renamed MEM_CGROUP_STAT_EVENTS to MEM_CGROUP_STAT_SOFTLIMIT, since really it's not a generic counter. Signed-off-by:
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Kirill A. Shutemov authored
Helper to get memory or mem+swap usage of the cgroup. Signed-off-by:
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Kirill A. Shutemov authored
This patchset introduces eventfd-based API for notifications in cgroups and implements memory notifications on top of it. It uses statistics in memory controler to track memory usage. Output of time(1) on building kernel on tmpfs: Root cgroup before changes: make -j2 506.37 user 60.93s system 193% cpu 4:52.77 total Non-root cgroup before changes: make -j2 507.14 user 62.66s system 193% cpu 4:54.74 total Root cgroup after changes (0 thresholds): make -j2 507.13 user 62.20s system 193% cpu 4:53.55 total Non-root cgroup after changes (0 thresholds): make -j2 507.70 user 64.20s system 193% cpu 4:55.70 total Root cgroup after changes (1 thresholds, never crossed): make -j2 506.97 user 62.20s system 193% cpu 4:53.90 total Non-root cgroup after changes (1 thresholds, never crossed): make -j2 507.55 user 64.08s system 193% cpu 4:55.63 total This patch: Introduce the write-only file "cgroup.event_control" in every cgroup. To register new notification handler you need: - create an eventfd; - open a control file to be monitored. Callbacks register_event() and unregister_event() must be defined for the control file; - write "<event_fd> <control_fd> <args>" to cgroup.event_control. Interpretation of args is defined by control file implementation; eventfd will be woken up by control file implementation or when the cgroup is removed. To unregister notification handler just close eventfd. If you need notification functionality for a control file you have to implement callbacks register_event() and unregister_event() in the struct cftype. [kamezawa.hiroyu@jp.fujitsu.com: Kconfig fix] Signed-off-by:
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Daisuke Nishimura authored
Try to reduce overheads in moving swap charge by: - Adds a new function(__mem_cgroup_put), which takes "count" as a arg and decrement mem->refcnt by "count". - Removed res_counter_uncharge, css_put, and mem_cgroup_put from the path of moving swap account, and consolidate all of them into mem_cgroup_clear_mc. We cannot do that about mc.to->refcnt. These changes reduces the overhead from 1.35sec to 0.9sec to move charges of 1G anonymous memory(including 500MB swap) in my test environment. Signed-off-by:
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Daisuke Nishimura authored
This patch is another core part of this move-charge-at-task-migration feature. It enables moving charges of anonymous swaps. To move the charge of swap, we need to exchange swap_cgroup's record. In current implementation, swap_cgroup's record is protected by: - page lock: if the entry is on swap cache. - swap_lock: if the entry is not on swap cache. This works well in usual swap-in/out activity. But this behavior make the feature of moving swap charge check many conditions to exchange swap_cgroup's record safely. So I changed modification of swap_cgroup's recored(swap_cgroup_record()) to use xchg, and define a new function to cmpxchg swap_cgroup's record. This patch also enables moving charge of non pte_present but not uncharged swap caches, which can be exist on swap-out path, by getting the target pages via find_get_page() as do_mincore() does. [kosaki.motohiro@jp.fujitsu.com: fix ia64 build] [akpm@linux-foundation.org: fix typos] Signed-off-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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Daisuke Nishimura authored
This move-charge-at-task-migration feature has extra charges on "to"(pre-charges) and "from"(left-over charges) during moving charge. This means unnecessary oom can happen. This patch tries to avoid such oom. Signed-off-by:
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Daisuke Nishimura authored
Try to reduce overheads in moving charge by: - Instead of calling res_counter_uncharge() against the old cgroup in __mem_cgroup_move_account() everytime, call res_counter_uncharge() at the end of task migration once. - removed css_get(&to->css) from __mem_cgroup_move_account() because callers should have already called css_get(). And removed css_put(&to->css) too, which was called by callers of move_account on success of move_account. - Instead of calling __mem_cgroup_try_charge(), i.e. res_counter_charge(), repeatedly, call res_counter_charge(PAGE_SIZE * count) in can_attach() if possible. - Instead of calling css_get()/css_put() repeatedly, make use of coalesce __css_get()/__css_put() if possible. These changes reduces the overhead from 1.7sec to 0.6sec to move charges of 1G anonymous memory in my test environment. Signed-off-by:
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Daisuke Nishimura authored
This patch is the core part of this move-charge-at-task-migration feature. It implements functions to move charges of anonymous pages mapped only by the target task. Implementation: - define struct move_charge_struct and a valuable of it(mc) to remember the count of pre-charges and other information. - At can_attach(), get anon_rss of the target mm, call __mem_cgroup_try_charge() repeatedly and count up mc.precharge. - At attach(), parse the page table, find a target page to be move, and call mem_cgroup_move_account() about the page. - Cancel all precharges if mc.precharge > 0 on failure or at the end of task move. [akpm@linux-foundation.org: a little simplification] Signed-off-by:
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Daisuke Nishimura authored
In current memcg, charges associated with a task aren't moved to the new cgroup at task migration. Some users feel this behavior to be strange. These patches are for this feature, that is, for charging to the new cgroup and, of course, uncharging from the old cgroup at task migration. This patch adds "memory.move_charge_at_immigrate" file, which is a flag file to determine whether charges should be moved to the new cgroup at task migration or not and what type of charges should be moved. This patch also adds read and write handlers of the file. This patch also adds no-op handlers for this feature. These handlers will be implemented in later patches. And you cannot write any values other than 0 to move_charge_at_immigrate yet. Signed-off-by:
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Li Zefan authored
Don't call get_pid_ns() before we locate/alloc the ns. Signed-off-by:
Paul Menage <menage@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:
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Ben Blum authored
Modify the Block I/O cgroup subsystem to be able to be built as a module. As the CFQ disk scheduler optionally depends on blk-cgroup, config options in block/Kconfig, block/Kconfig.iosched, and block/blk-cgroup.h are enhanced to support the new module dependency. Signed-off-by:
Ben Blum <bblum@andrew.cmu.edu> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Paul Menage <menage@google.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by:
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Kirill A. Shutemov authored
Add a forgotten item into CONTENTS. Signed-off-by:
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Ben Blum authored
Provides support for unloading modular subsystems. This patch adds a new function cgroup_unload_subsys which is to be used for removing a loaded subsystem during module deletion. Reference counting of the subsystems' modules is moved from once (at load time) to once per attached hierarchy (in parse_cgroupfs_options and rebind_subsystems) (i.e., 0 or 1). Signed-off-by:
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Ben Blum authored
Add interface between cgroups subsystem management and module loading This patch implements rudimentary module-loading support for cgroups - namely, a cgroup_load_subsys (similar to cgroup_init_subsys) for use as a module initcall, and a struct module pointer in struct cgroup_subsys. Several functions that might be wanted by modules have had EXPORT_SYMBOL added to them, but it's unclear exactly which functions want it and which won't. Signed-off-by:
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Ben Blum authored
This patch series provides the ability for cgroup subsystems to be compiled as modules both within and outside the kernel tree. This is mainly useful for classifiers and subsystems that hook into components that are already modules. cls_cgroup and blkio-cgroup serve as the example use cases for this feature. It provides an interface cgroup_load_subsys() and cgroup_unload_subsys() which modular subsystems can use to register and depart during runtime. The net_cls classifier subsystem serves as the example for a subsystem which can be converted into a module using these changes. Patch #1 sets up the subsys[] array so its contents can be dynamic as modules appear and (eventually) disappear. Iterations over the array are modified to handle when subsystems are absent, and the dynamic section of the array is protected by cgroup_mutex. Patch #2 implements an interface for modules to load subsystems, called cgroup_load_subsys, similar to cgroup_init_subsys, and adds a module pointer in struct cgroup_subsys. Patch #3 adds a mechanism for unloading modular subsystems, which includes a more advanced rework of the rudimentary reference counting introduced in patch 2. Patch #4 modifies the net_cls subsystem, which already had some module declarations, to be configurable as a module, which also serves as a simple proof-of-concept. Part of implementing patches 2 and 4 involved updating css pointers in each css_set when the module appears or leaves. In doing this, it was discovered that css_sets always remain linked to the dummy cgroup, regardless of whether or not any subsystems are actually bound to it (i.e., not mounted on an actual hierarchy). The subsystem loading and unloading code therefore should keep in mind the special cases where the added subsystem is the only one in the dummy cgroup (and therefore all css_sets need to be linked back into it) and where the removed subsys was the only one in the dummy cgroup (and therefore all css_sets should be unlinked from it) - however, as all css_sets always stay attached to the dummy cgroup anyway, these cases are ignored. Any fix that addresses this issue should also make sure these cases are addressed in the subsystem loading and unloading code. This patch: Make subsys[] able to be dynamically populated to support modular subsystems This patch reworks the way the subsys[] array is used so that subsystems can register themselves after boot time, and enables the internals of cgroups to be able to handle when subsystems are not present or may appear/disappear. Signed-off-by:
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