Arm Linux Kernel Hacks

From callstack, "ndroid.systemui" process is executing inside arch_spin_lock() function. And then watchdog reset is triggered.

-000|aee_wdt_atf_entry()

-001|prefetchw(inline)

-001|arch_spin_lock(inline)

-001|do_raw_spin_lock_flags(inline)

-001|__raw_spin_lock_irqsave(inline)

-001|raw_spin_lock_irqsave(lock = 0xDD82725C)

-002|__wake_up(q = 0xDD82725C, mode = 1, nr_exclusive = 1, key = 0x0)

-003|mmc_wait_data_done

-004|msdc_irq_data_complete(host = 0xDD827280, ?, error = 0)

-005|msdc_irq(?, dev_id = 0xDD13B9C8)

-006|static_key_count(inline)

-006|static_key_false(inline)

-006|trace_irq_handler_exit(inline)

-006|handle_irq_event_percpu(?, action = 0xDD13B9C8)

-007|handle_irq_event(desc = 0xC0F38440)

-008|cond_unmask_eoi_irq(inline)

-008|handle_fasteoi_irq(?, desc = 0xC0F38440)

-009|static_key_count(inline)

-009|static_key_false(inline)

-009|trace_irq_exit(inline)

-009|__handle_domain_irq(domain = 0xDE806000, hwirq = 111, lookup = TRUE, ?)

-010|__raw_readl(inline)

-010|gic_handle_irq(regs = 0xDD13BFB0)

-011|__irq_usr(asm)

Now, it is time to analyze the spinlock field first. Looking at spinlock instance 0xDD82725C, the each owner and next filed is as below.

[owner: 0x56AC, next: 0x56AD]

(raw_spinlock_t *)0xDD82725C = 0xDD82725C -> (

  raw_lock = (

    slock = 0x56AD56AB,

       tickets = (

         owner = 0x56AB, // <<--

         next = 0x56AD))) // <<--

The fact that next field is larger than owner means the other process already acquired spinlock beforehand.

When scanning memory dump who is accessing  0xDD82725C spinlock instance, several candidate processes can be seen as below.

(where)

(raw_spinlock_t *)0xDD82725C

c2d01b78: dd82725c

c2d01b7c: dd82725c

c44f0994: dd82725c

dd13bd60: dd82725c // "ndroid.systemui"

dd13bd9c: dd82725c // "ndroid.systemui"

dd13bdc8: dd82725c // "ndroid.systemui"

ddbefdb8: dd82725c // <<--"mmcqd/0"

ddbefdd0: dd82725c

e0abd994: dd82725c

From the candidate list above, "mmcqd/0" is accessing  0xDD82725C spinlock instance.

v.v % (struct thread_info*)(0xDDBEFDB8 & ~0x1fff)

  (long unsigned int) swap_in = 0 = 0x0 = '....',

  (long unsigned int) swap_out = 0 = 0x0 = '....',

  (struct task_cputime) cputime_expires = ((cputime_t) utime = 0 = 0x0 = '....', (cputime_t) stime = 0 = 0x0 = '....', (long lo

  (struct list_head [3]) cpu_timers = ([0] = ((struct list_head *) next = 0xDDB49A08 = -> ((struct list_head *) next = 0xDDB49

  (struct cred *) real_cred = 0xDDB71200 = -> ((atomic_t) usage = ((int) counter = 2 = 0x2 = '....'), (kuid_t) uid = ((uid_t)

  (struct cred *) cred = 0xDDB71200 = -> ((atomic_t) usage = ((int) counter = 2 = 0x2 = '....'), (kuid_t) uid = ((uid_t) val =

   (char [16]) comm = "mmcqd/0",

The callstacks of "mmcqd/0" process can be observed as follows. 

-000|schedule()

-001|mmc_wait_for_data_req_done(inline)

-001|mmc_start_req(host = 0xC0F75D0C, areq = 0xC0F644E0, error = 0xC102CB08)

-002|mmc_blk_issue_rw_rq(mq = 0xDDB64408, rqc = 0x0)

-003|mmc_blk_issue_rq(mq = 0xDDB64408, req = 0x0)

-004|mmc_queue_thread(d = 0xDDB64408)

-005|kthread(_create = 0xDDB8BDC0)

-006|ret_from_fork(asm)

-007|ret_fast_syscall(asm)

Looking into mmc_wait_for_data_req_done(), the spinlock is acquired using spin_lock_irqsave(&context_info->lock, flags).

static int mmc_wait_for_data_req_done(struct mmc_host *host,

struct mmc_request *mrq,

struct mmc_async_req *next_req)

{

    struct mmc_command *cmd;

    struct mmc_context_info *context_info = &host->context_info;

    int err;

    unsigned long flags;

    while (1) {

        wait_event_interruptible(context_info->wait,

                                               (context_info->is_done_rcv ||

                                               context_info->is_new_req));

        spin_lock_irqsave(&context_info->lock, flags);

        context_info->is_waiting_last_req = false;

Looking into code snippet more, below functions are executed among callbacks of "ndroid.systemui" processes.

-003|mmc_wait_data_done

-004|msdc_irq_data_complete(host = 0xDD827280, ?, error = 0)

mmc_wait_data_done() 함수를 보면 mrq->host->context_info.is_done_rcv = true로 설정하고,

&mrq->host->context_info.wait wait queue을 깨우는 역할을 수행했다.

static void mmc_wait_data_done(struct mmc_request *mrq){

    mrq->host->context_info.is_done_rcv = true;

     wake_up_interruptible(&mrq->host->context_info.wait);

}

그런데 mmc_wait_for_data_req_done() 함수의 아래 구문은 context_info->is_done_rcv, context_info->is_new_req가 true가

될 때 까지 기다리는 코드다.

wait_event_interruptible(context_info->wait,

  (context_info->is_done_rcv ||

  context_info->is_new_req));

정리해보면, race condition으로 wake_up_interruptible(&mrq->host->context_info.wait); 함수를 통해 wait_queue에 queue된 

&mrq->host->context_info.wait으로 등록된 프로세스를 깨우기 전에 아래 구문이 풀려버려 이미 깨어버린 경우임을 짐작할 수 있다.

잠을 자고 있는 누군가를 깨우려고 손을 대려고 하는데 이미 깨버린 경우와 비슷하네.

In-depth Analysis

내 추정이 맞다면 아래 코드를 삽입하면 바로 커널 패닉이 나야 한다.

(램덤프 force_mmc_wait_data_done_crash)

static void mmc_wait_data_done(struct mmc_request mrq){*

    mrq->host->context_info.is_done_rcv = true;

    + mdelay(1);

    wake_up_interruptible(&mrq->host->context_info.wait);

}

그런데 바로 커널 패닉이 발생했다.

-000|do_DataAbort(addr = 0, fsr = 0, regs = 0x0)

-001|__dabt_svc(asm)

-->|exception

-002|debug_spin_lock_before(inline)

-002|do_raw_spin_lock(lock = 0x02B4)

-003|raw_spin_lock_irqsave(lock = 0x02B4)

-004|__wake_up(q = 0x02B4, mode = 1, nr_exclusive = 1, key = 0x0)

-005|mmc_wait_data_done(mrq = 0xDC9725F8)

-006|msdc_irq_data_complete(host = 0xDC919300, ?, error = 0)

-007|msdc_irq(?, dev_id = 0x1)

-008|handle_irq_event_percpu(?, action = 0xDC91E0C0)

-009|handle_irq_event(desc = 0xC121A440)

-010|cond_unmask_eoi_irq(inline)

-010|handle_fasteoi_irq(?, desc = 0xC121A440)

-011|static_key_count(inline)

-011|static_key_false(inline)

-011|trace_irq_exit(inline)

-011|__handle_domain_irq(domain = 0xDE806000, hwirq = 111, lookup = TRUE, ?)

-012|__raw_readl(inline)

-012|gic_handle_irq(regs = 0xCB773E10)

-013|__irq_svc(asm)

-->|exception

-014|current_thread_info(inline)

-014|check_preemption_disabled(what1 = 0xC0F115AC, what2 = 0xC0EE0B28)

-015|debug_smp_processor_id()

-016|MT_trace_preempt_on()

-017|preempt_count_sub

-018|current_thread_info(inline)

-018|preempt_count(inline)

-018|should_resched(inline)

-018|__percpu_counter_add(fbc = 0xD8AC7178, amount = 0, batch = 32)

-019|__sb_start_write(sb = 0xC0F115AC, level = -1058141400, wait = FALSE)

-020|file_start_write(inline)

-020|vfs_write(file = 0xD366C480, buf = 0xBEA83A4C, ?, pos = 0xCB773F78)

-021|SYSC_write(inline)

-021|sys_write(?, buf = -1096271284, count = 146)

-022|ret_fast_syscall(asm)

mrq->host->context_info.wait 변수를 확인해보면, 이미 mrq->host 변수가 0이다.

(struct mmc_request *)0xDC9725F8 = 0xDC9725F8 -> (

    sbc = 0xDC97262C,

    cmd = 0xDC972660,

    data = 0xDC9726C8,

    stop = 0xDC972694,

    completion = (done = 0x0, wait = (lock = (rlock = (raw_lock = (slock = 0x0,

      done = 0x0,

     host = 0x0)

어머 그런데, mmcqd/0 프로세스가 mmc_wait_for_data_req_done() 코드를 이미 수행했네?

-000|context_switch(inline)

-000|__schedule()

-001|schedule()

-002|mmc_wait_for_data_req_done(inline)

-002|mmc_start_req(host = 0xDC919000, areq = 0xDC972710, ?)

-003|mmc_blk_issue_rw_rq(mq = 0x0, rqc = 0xC64B18C0)

-004|mmc_blk_issue_rq(mq = 0xDC972494, req = 0xC64B18C0)

-005|mmc_queue_thread(d = 0xDC972494)

-006|kthread(_create = 0xDCA24E40)

-007|ret_from_fork(asm)

-008|ret_fast_syscall(asm)

@ftrace log를 좀 더 추가해보자.

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c

index db74413..fcf6692 100644

? a/drivers/mmc/core/core.c

+++ b/drivers/mmc/core/core.c

@@ -1034,6 +1034,9 @@ out:

}

EXPORT_SYMBOL(mmc_start_bkops);

#endif

/*

mmc_wait_data_done() - done callback for data request

@mrq: done data request

@@ -1042,10 +1045,25 @@ EXPORT_SYMBOL(mmc_start_bkops);

*/

static void mmc_wait_data_done(struct mmc_request *mrq)

static void mmc_wait_data_done(struct mmc_request mrq) *{

        mrq->host->context_info.is_done_rcv = true;

+      trace_printk("+msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

        mdelay(1);

+      trace_printk("++msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

        wake_up_interruptible(&mrq->host->context_info.wait);

+      trace_printk("--msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

역시나 GIC mtk-msdc(111) IRQ가 Trigger된 다음에 아래와 같이 커널 패닉이 발생하였네.

(램덤프: neo_more_crash_ftrace)

-000|do_DataAbort(addr = 0, fsr = 0, regs = 0x0)

-001|__dabt_svc(asm)

-->|exception

-002|debug_spin_lock_before(inline)

-002|do_raw_spin_lock(lock = 0x02B4)

-003|raw_spin_lock_irqsave(lock = 0x02B4)

-004|__wake_up(q = 0x02B4, mode = 1, nr_exclusive = 1, key = 0x0)

-005|mmc_wait_data_done(mrq = 0xDC9235F8)

-006|msdc_irq_data_complete(host = 0xDC927300, ?, error = 0)

-007|msdc_irq(?, dev_id = 0x1)

-008|handle_irq_event_percpu(?, action = 0xDC92B180)

-009|handle_irq_event(desc = 0xC121A440)

-010|cond_unmask_eoi_irq(inline)

-010|handle_fasteoi_irq(?, desc = 0xC121A440)

-011|static_key_count(inline)

-011|static_key_false(inline)

-011|trace_irq_exit(inline)

-011|__handle_domain_irq(domain = 0xDE806000, hwirq = 111, lookup = TRUE, ?)

-012|__raw_readl(inline)

-012|gic_handle_irq(regs = 0xC2631E20)

-013|__irq_svc(asm)

-->|exception

-014|__fget(?, mask = 16384)

-015|__fget_light(?, mask = 16384)

-016|__fdget

-017|sockfd_lookup_light(?, err = 0xC2631EC8, fput_needed = 0xC2631ECC)

-018|SYSC_recvfrom(inline)

-018|sys_recvfrom(?, ubuf = -1212542344, ?, flags = 64, addr = 0, addr_len = 0)

-019|ret_fast_syscall(asm)

Ftrace log 분석 좀 해보자.

커널 패닉이 일어나기 직전 상황

[1]: irq=111 name=mtk-msdc 가 Trigger됨

[2]: IRQ context에서 mmc_wait_data_done() 함수가 호출 from(msdc_irq_data_complete)

[2]~[3] 사이 mmcq0 process가 context switching 되지 않고 수행 ( InputDispatcher-1538)

[3]: mdelay(1); 이후 찍히는 ftrace log

[4]: wake_up_interruptible(&mrq->host->context_info.wait); API 호출로 mmcq0 process을 wakeup 시킴

CPU5: mmcqd/0, pid=244

sched_wakeup: comm=mmcqd/0 pid=244 prio=120 success=1 target_cpu=005 state=W

[5]: wake_up_interruptible(&mrq->host->context_info.wait); API 호출이 끝난 후 찍히는 로그(별 의미 없음)

kworker/4:0-25 [004] 149.827488: irq_handler_entry: irq=111 name=mtk-msdc // <<--[1]

kworker/4:0-25 [004] 149.827495: bprint: mmc_wait_data_done: +msdc [F: mmc_wait_data_done, L:1049]: ? ? from(msdc_irq_data_complete) // <<--[2]

InputDispatcher-1538 [005] 149.827496: sched_migrate_task: comm=m.lge.launcher3 pid=2135 prio=120 orig_cpu=6 dest_cpu=4 state=W

InputDispatcher-1538 [005] 149.827519: sched_wakeup: comm=m.lge.launcher3 pid=2135 prio=120 success=1 target_cpu=004 state=W

InputDispatcher-1538 [005] 149.827591: sched_migrate_task: comm=ndroid.systemui pid=1622 prio=120 orig_cpu=5 dest_cpu=6 state=W

InputDispatcher-1538 [005] 149.827608: sched_wakeup: comm=ndroid.systemui pid=1622 prio=120 success=1 target_cpu=006 state=W

InputDispatcher-1538 [005] 149.827675: sched_migrate_task: comm=android.ui pid=1287 prio=118 orig_cpu=4 dest_cpu=6 state=W

InputDispatcher-1538 [005] 149.827694: sched_wakeup: comm=android.ui pid=1287 prio=118 success=1 target_cpu=006 state=W

InputDispatcher-1538 [005] 149.827855: sched_switch: prev_comm=InputDispatcher prev_pid=1538 prev_prio=112 prev_state=S ==> next_comm=swapper/5 next_pid=0 next_prio=120 extra_prev_state=K|m|d 

<idle>-0 [005] 149.827912: sched_switch: prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=InputDispatcher next_pid=1538 next_prio=112 extra_prev_state=K|m|d 

InputDispatcher-1538 [005] 149.828064: sched_switch: prev_comm=InputDispatcher prev_pid=1538 prev_prio=112 prev_state=S ==> next_comm=swapper/5 next_pid=0 next_prio=120 extra_prev_state=K|m|d 

<idle>-0 [005] 149.828209: sched_switch: prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=InputDispatcher next_pid=1538 next_prio=112 extra_prev_state=K|m|d 

InputDispatcher-1538 [005] 149.828352: sched_switch: prev_comm=InputDispatcher prev_pid=1538 prev_prio=112 prev_state=S ==> next_comm=swapper/5 next_pid=0 next_prio=120 extra_prev_state=K|m|d 

kworker/4:0-25 [004] 149.828497: bprint: mmc_wait_data_done: ++msdc [F: mmc_wait_data_done, L:1058]: ? ? from(msdc_irq_data_complete) // <<--[3]

kworker/4:0-25 [004] 149.828521: sched_wakeup: comm=mmcqd/0 pid=244 prio=120 success=1 target_cpu=005 state=W // <<--[4]

kworker/4:0-25 [004] 149.828525: bprint: mmc_wait_data_done: -msdc [F: mmc_wait_data_done, L:1060]: ? ? from(msdc_irq_data_complete) <<-[5]

<idle>0 [005] 149.828528: sched_switch: prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=mmcqd/0 next_pid=244 next_prio=120 extra_prev_state=K|m|d <<-[6]

kworker/4:0-25 [004] 149.828530: irq_handler_exit: irq=111 ret=handled

1046 static void mmc_wait_data_done(struct mmc_request *mrq)

1047*{*

1048 mrq->host->context_info.is_done_rcv = true;

1049 trace_printk("+msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[2]

//생략

1051 mdelay(1);

//생략

1057

1058 trace_printk("++msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[3]

1059 wake_up_interruptible(&mrq->host->context_info.wait);

1060 trace_printk("-msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<-[5]

커널 패닉 상황

[7]: irq=111 name=mtk-msdc 가 handle 되었음

[8]: [mmcqd/0-244, CPU5]mmc_wait_for_data_req_done() 함수 내[from(mmc_blk_issue_rw_rq)] wait_event_interruptible()에서 빠져나옴.

[9][10]: [mmcqd/0-244, CPU5]mmc_wait_for_data_req_done() 함수를 빠져나옴

[11]: irq=111 name=mtk-msdc 가 Trigger됨 --> CPU4의 m.lge.launcher3-2135

[12]: [mmcqd/0-244, CPU5] 깨어난 mmcqd/0-244 프로세스 활동 시작

&mqrq->brq 변수를 0으로 밀어버림 (where: memset(brq, 0, sizeof(struct mmc_blk_request));

[13]: [m.lge.launcher3-2135 CPU4] irq=111 name=mtk-msdc IRQ로 Trigger되어 실행되어

mmc_wait_data_done() 함수 진입 

[14][15]: [mmcqd/0-244, CPU5] mmc_blk_rw_rq_prep() 함수 퇴장하려함

[16][17][18] [mmcqd/0-244, CPU5] mmc_wait_for_data_req_done() 함수 처리 후 퇴장하려함

[19]: [m.lge.launcher3-2135 CPU4] wake_up_interruptible(&mrq->host->context_info.wait);

[20] 커널 패닉

[12]번 동작에서 0으로 초기화된 &mrq->host 변수를 통해 밀린((where: memset(brq, 0, sizeof(struct mmc_blk_request)) wake_up_interruptible() API 호출

kworker/4:0-25 [004] 149.828530: irq_handler_exit: irq=111 ret=handled // <<--[7]

mmcqd/0-244 [005] 149.828536: bprint: mmc_start_req: ++mmcq [F: mmc_wait_for_data_req_done, L:1236]: ? ? from(mmc_blk_issue_rw_rq) // <<--[8]

kworker/4:0-25 [004] 149.828537: irq_handler_entry: irq=30 name=arch_timer

kworker/4:0-25 [004] 149.828546: irq_handler_exit: irq=30 ret=handled

mmcqd/0-244 [005] 149.828559: bprint: mmc_start_req: mmcq [F: mmc_wait_for_data_req_done, L:1268]: ? ? from(mmc_blk_issue_rw_rq) // <<-[9]

mmcqd/0-244 [005] 149.828561: bprint: mmc_start_req: mmcq release [F: mmc_wait_for_data_req_done, L:1270]: ? ? from(mmc_blk_issue_rw_rq) // <<--[10]

kworker/4:0-25 [004] 149.828584: workqueue_execute_end: work struct 0xcb40cae4

kworker/4:0-25 [004] 149.828630: sched_switch: prev_comm=kworker/4:0 prev_pid=25 prev_prio=120 prev_state=S ==> next_comm=m.lge.launcher3 next_pid=2135 next_prio=120 extra_prev_state=K|m|d 

m.lge.launcher3-2135 [004] 149.828660: irq_handler_entry: irq=111 name=mtk-msdc // <<--[11]

mmcqd/0-244 [005] 149.828661: bprint: mmc_blk_rw_rq_prep: ++mmc_blk_rw_rq_prep [F: mmc_blk_rw_rq_prep, L:1725]: ? ? from(mmc_blk_issue_rw_rq) // <<--[12]

m.lge.launcher3-2135 [004] 149.828666: bprint: mmc_wait_data_done: +msdc [F: mmc_wait_data_done, L:1049]: ? ? from(msdc_irq_data_complete) // <<--[13]

mmcqd/0-244 [005] 149.828670: bprint: mmc_blk_rw_rq_prep: -mmc_blk_rw_rq_prep [F: mmc_blk_rw_rq_prep, L:1905]: ? ? from(mmc_blk_issue_rw_rq) // <<-[14]

mmcqd/0-244 [005] 149.828672: bprint: mmc_blk_rw_rq_prep: mmc_blk_rw_rq_prep [F: mmc_blk_rw_rq_prep, L:1907]: ? ? from(mmc_blk_issue_rw_rq) // <<-[15]

mmcqd/0-244 [005] 149.828681: bprint: mmc_start_req: +mmcq [F: mmc_wait_for_data_req_done, L:1231]: ? ? from(mmc_blk_issue_rw_rq) // <<--[16]

mmcqd/0-244 [005] 149.828683: bprint: mmc_start_req: ++mmcq [F: mmc_wait_for_data_req_done, L:1236]: ? ? from(mmc_blk_issue_rw_rq) // <<--[17]

mmcqd/0-244 [005] 149.828695: bprint: mmc_start_req: -mmcq [F: mmc_wait_for_dat뗥nQ, L:0]: ? ? from(0x726f776bS) // <<--[18]

m.lge.launcher3-2135 [004] 149.829669: bprint: mmc_wait_data_done: ++msdc [F: mmc_wait_data_done, L:1058]: ? ? from(msdc_irq_data_complete) // <<--[19]

m.lge.launcher3-2135 [004] 149.829748: tracing_on: ftrace is disabled caller=oops_enter // <<?[20]

1222 static int mmc_wait_for_data_req_done(struct mmc_host *host,

1223 struct mmc_request *mrq,

1224 struct mmc_async_req *next_req)

1225*{*

1226 struct mmc_command *cmd;

1227 struct mmc_context_info *context_info = &host->context_info;

1228 int err;

1229 unsigned long flags;

1230

1231 trace_printk("+mmcq [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[16]

1232 while (1) {

1233 wait_event_interruptible(context_info->wait,

1234 (context_info->is_done_rcv ||

1235 context_info->is_new_req));

1236 trace_printk("++mmcq [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[8], [17]

1237 spin_lock_irqsave(&context_info->lock, flags);

//snip

1268 trace_printk("mmcq [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<-[9], [18]

1269 mmc_retune_release(host);

1270 trace_printk("mmcq release [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

1271 return err;

1272 }

1701 static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,

1702 struct mmc_card *card,

1703 int disable_multi,

1704 struct mmc_queue *mq)

1705*{*

1706 u32 readcmd, writecmd;

1707 struct mmc_blk_request *brq = &mqrq->brq;

//생략

1724 memset(brq, 0, sizeof(struct mmc_blk_request));

1725 trace_printk("++mmc_blk_rw_rq_prep [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[12]

1726 brq->mrq.cmd = &brq->cmd;

//생략

1905 trace_printk("-mmc_blk_rw_rq_prep [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); //<<-[14]

1906 mmc_queue_bounce_pre(mqrq);

1907 trace_printk("-mmc_blk_rw_rq_prep [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

1908 }

1046 static void mmc_wait_data_done(struct mmc_request *mrq)

1047*{*

1048 mrq->host->context_info.is_done_rcv = true;

1049 trace_printk("+msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[13]

//생략

1051 mdelay(1);

//생략

1057

1058 trace_printk("++msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0)); // <<--[19]

1059 wake_up_interruptible(&mrq->host->context_info.wait);

1060 trace_printk("--msdc [F: %s, L:%d]: ? ? from(%pS)\n", _func,LINE, (void *)_builtin_return_address(0));

정리하면 wake_up_interruptible() API에 파라미터로 전달되는 &mrq->host->context_info.wait를 다른 값(mmcqd를 깨울 수 있는 wait_queue)으로 바꾸거나,

wake_up_interruptible() 호출 시 조건을 줘야 한다. 혹은 spinlock irq save로 코드 보호

솔류션

분석된 내용에 따라 아래 패치를 적용하였더니 문제가 사라졌다. 

 diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c

index c3abe34..01e4bfc 100644

--- a/drivers/mmc/core/core.c

+++ b/drivers/mmc/core/core.c

@@ -403,8 +403,13 @@ EXPORT_SYMBOL(mmc_start_bkops);

*/

static void mmc_wait_data_done(struct mmc_request *mrq)

{

+       unsigned long flags;

+       struct mmc_context_info *context_info = &mrq->host->context_info;

+

+       spin_lock_irqsave(&context_info->lock, flags);

         mrq->host->context_info.is_done_rcv = true;

         wake_up_interruptible(&mrq->host->context_info.wait);

+       spin_unlock_irqrestore(&context_info->lock, flags);

}

static void mmc_wait_done(struct mmc_request *mrq)

@@ -465,6 +470,7 @@ static int mmc_wait_for_data_req_done(struct mmc_host *host,

         struct mmc_command *cmd;

         struct mmc_context_info *context_info = &host->context_info;

         int err;

+       bool is_done_rcv = false;

         unsigned long flags;

         while (1) {

@@ -472,9 +478,10 @@ static int mmc_wait_for_data_req_done(struct mmc_host *host,

        (context_info->is_done_rcv ||

                     context_info->is_new_req));

                     spin_lock_irqsave(&context_info->lock, flags);

+          is_done_rcv = context_info->is_done_rcv;

            context_info->is_waiting_last_req = false;

            spin_unlock_irqrestore(&context_info->lock, flags);

-          if (context_info->is_done_rcv) {

+         if (is_done_rcv) {

                  context_info->is_done_rcv = false;

                  context_info->is_new_req = false;

                  cmd = mrq->cmd;

By the way, relevant patch has been already released inside Linux Kernel Community. 

https://patchwork.kernel.org/patch/7089351/

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c

index 347108a..db74413 100644

--- a/drivers/mmc/core/core.c

+++ b/drivers/mmc/core/core.c

@@ -1042,8 +1042,10 @@ EXPORT_SYMBOL(mmc_start_bkops);

*/

static void mmc_wait_data_done(struct mmc_request *mrq)

{

-       mrq->host->context_info.is_done_rcv = true;

-       wake_up_interruptible(&mrq->host->context_info.wait);

+      struct mmc_context_info *context_info = &mrq->host->context_info;

+

+      context_info->is_done_rcv = true;

+      wake_up_interruptible(&context_info->wait);

}