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ldd ch06: use Opaque instead of Mutex in Arc
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It uses Opaque type to get the mutable reference to an object
inside of super object wrapped with Arc.
Opaque::raw_get() function returns mutable pointer.

But it still has a problem as below.
A spinlock in the completion object might not be initialized correctly.

/ # insmod share/rust_ldd06.ko
[    8.838768] rust_ldd06: module verification failed: signature and/or required key missing - tal
[    8.841700] rust_completion: rust_ldd06 is loaded
[    8.842994] rust_completion: completion_dev created
/ # mknod /dev/rust_ldd06 c 10 124
/ # cat /dev/rust_ldd06 &
/ # [   28.024130] rust_completion: open is invoked
[   28.025404] rust_completion: read is invoked

/ # echo "asdf" > /dev/rust_ldd06
[   34.750500] rust_completion: open is invoked
[   34.751870] rust_completion: write is invoked
[   34.753140] BUG: unable to handle page fault for address: ffffc90000594743
[   34.754996] #PF: supervisor write access in kernel mode
[   34.756442] #PF: error_code(0x0002) - not-present page
[   34.757111] PGD 3000067 P4D 3000067 PUD 31a7067 PMD 414b067 PTE 0
[   34.757111] Oops: 0002 [#1] PREEMPT SMP NOPTI
[   34.757111] CPU: 0 PID: 1 Comm: sh Tainted: G            E      6.6.0-rc4+ Rust-for-Linux#76
[   34.757111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[   34.757111] RIP: 0010:_raw_spin_lock_irqsave+0x32/0xa0
[   34.757111] Code: e5 41 57 41 56 41 54 53 49 89 ff 9c 58 0f 1f 40 00 49 89 c6 fa 0f 1f 44 00 01
[   34.757111] RSP: 0018:ffffc9000000bd30 EFLAGS: 00010046
[   34.757111] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
[   34.757111] RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffffc90000594743
[   34.757111] RBP: ffffc9000000bd50 R08: 0000000000000000 R09: 0000000000000000
[   34.757111] R10: ffffc9000000bca8 R11: 3fffffffffffffff R12: 0000000000000000
[   34.757111] R13: 0000000000000005 R14: 0000000000000097 R15: ffffc90000594743
[   34.757111] FS:  0000000001d1c3c0(0000) GS:ffff888007a00000(0000) knlGS:0000000000000000
[   34.757111] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   34.757111] CR2: ffffc90000594743 CR3: 0000000004322000 CR4: 00000000000006f0
[   34.757111] Call Trace:
[   34.757111]  <TASK>
[   34.757111]  ? __die_body+0x6b/0xb0
[   34.757111]  ? __die+0x9b/0xb0
[   34.757111]  ? page_fault_oops+0x24c/0x370
[   34.757111]  ? prb_read_valid+0x19/0x20
[   34.757111]  ? printk_get_next_message+0x72/0x320
[   34.757111]  ? kernelmode_fixup_or_oops+0xd7/0x100
[   34.757111]  ? __bad_area_nosemaphore+0x69/0x290
[   34.757111]  ? io_serial_in+0x50/0x50
[   34.757111]  ? bad_area_nosemaphore+0x16/0x20
[   34.757111]  ? do_kern_addr_fault+0x7c/0x90
[   34.757111]  ? exc_page_fault+0xcf/0xf0
[   34.757111]  ? asm_exc_page_fault+0x27/0x30
[   34.757111]  ? _raw_spin_lock_irqsave+0x32/0xa0
[   34.757111]  try_to_wake_up+0x46/0x860
[   34.757111]  ? vprintk+0x52/0x60
[   34.757111]  ? _printk+0x4b/0x50
[   34.757111]  complete+0x4c/0x80
[   34.757111]  _RNvMs3_NtCshlmskAEPslc_6kernel4fileINtB5_16OperationsVtableINtNtB7_7miscdev12Reg]
[   34.757111]  vfs_write+0x111/0x3d0
[   34.757111]  ? handle_mm_fault+0x1e5/0x2e0
[   34.757111]  ksys_write+0x5f/0xb0
[   34.757111]  __x64_sys_write+0x1b/0x20
[   34.757111]  do_syscall_64+0x35/0x50
[   34.757111]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[   34.757111] RIP: 0033:0x4ad317
[   34.757111] Code: ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04
[   34.757111] RSP: 002b:00007ffc77a92d48 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[   34.757111] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00000000004ad317
[   34.757111] RDX: 0000000000000005 RSI: 0000000001d21a50 RDI: 0000000000000001
[   34.757111] RBP: 0000000001d21a50 R08: fefefefefefefeff R09: feff86ff65637260
[   34.757111] R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000005
[   34.757111] R13: 0000000001d1c3a0 R14: 00007ffc77a92f01 R15: 00007ffc77a92db0
[   34.757111]  </TASK>
[   34.757111] Modules linked in: rust_ldd06(E)
[   34.757111] CR2: ffffc90000594743
[   34.757111] ---[ end trace 0000000000000000 ]---
[   34.757111] RIP: 0010:_raw_spin_lock_irqsave+0x32/0xa0
[   34.757111] Code: e5 41 57 41 56 41 54 53 49 89 ff 9c 58 0f 1f 40 00 49 89 c6 fa 0f 1f 44 00 01
[   34.757111] RSP: 0018:ffffc9000000bd30 EFLAGS: 00010046
[   34.757111] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
[   34.757111] RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffffc90000594743
[   34.757111] RBP: ffffc9000000bd50 R08: 0000000000000000 R09: 0000000000000000
[   34.757111] R10: ffffc9000000bca8 R11: 3fffffffffffffff R12: 0000000000000000
[   34.757111] R13: 0000000000000005 R14: 0000000000000097 R15: ffffc90000594743
[   34.757111] FS:  0000000001d1c3c0(0000) GS:ffff888007a00000(0000) knlGS:0000000000000000
[   34.757111] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   34.757111] CR2: ffffc90000594743 CR3: 0000000004322000 CR4: 00000000000006f0
[   34.757111] note: sh[1] exited with irqs disabled
[   34.818149] note: sh[1] exited with preempt_count 3
[   34.818663] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
[   34.819478] Kernel Offset: disabled
[   34.819864] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]-
QEMU 6.2.0 monitor - type 'help' for more information

Signed-off-by: Gioh Kim <[email protected]>
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gurugio committed Oct 30, 2023
1 parent 62b89d6 commit c038d5a
Showing 1 changed file with 6 additions and 24 deletions.
30 changes: 6 additions & 24 deletions samples/rust/rust_ldd06.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ use kernel::{
io_buffer::{IoBufferReader, IoBufferWriter},
miscdev, new_mutex, pin_init,
sync::{Arc, ArcBorrow, Mutex},
types::Opaque,
};

module! {
Expand All @@ -29,22 +30,11 @@ module! {
license: "GPL",
}

// Fist I made CompletionDev { completion: bindings::completion }.
// But it didn't work because we cannot get mutable reference to CompletionDev in read/write functions.
// The argument of read/write functions is ArcBorrow<'_, CompletionDev>.
// So it's not allowed to get the mutable reference to CompletionDev.
// The only way to mutate through ArcBorrow is to use Mutex/RwLock/Atomic types.
// (see doc.rust-lang.org/std/sync/struct.Mutex.html)
// Finally I makde CompletionInner struct and put it into Mutex.
struct CompletionInner {
completion: bindings::completion,
}

// internal info between file operations
#[pin_data]
struct CompletionDev {
#[pin]
inner: Mutex<CompletionInner>,
completion: Opaque<bindings::completion>,
}

// TODO: impl CompletionDev::try_new
Expand All @@ -63,17 +53,11 @@ impl CompletionDev {
let mut key: bindings::lock_class_key = bindings::lock_class_key::default();
compl.done = 0;
unsafe {
bindings::__init_swait_queue_head(
&mut compl.wait,
compl_name.as_char_ptr() as *mut core::ffi::c_char,
&mut key,
);
bindings::__init_swait_queue_head(&mut compl.wait, compl_name.as_char_ptr(), &mut key);
}

let dev = Arc::pin_init(pin_init!(Self {
inner <- new_mutex!(CompletionInner {
completion: compl,
}),
completion: Opaque::new(compl),
}))?;

Ok(dev)
Expand Down Expand Up @@ -105,9 +89,8 @@ impl file::Operations for RustFile {
) -> Result<usize> {
pr_info!("read is invoked\n");

let mut inner_guard = shared.inner.lock();
unsafe {
bindings::wait_for_completion(&mut inner_guard.completion);
bindings::wait_for_completion(Opaque::raw_get(&shared.completion));
}

Ok(0)
Expand All @@ -121,9 +104,8 @@ impl file::Operations for RustFile {
) -> Result<usize> {
pr_info!("write is invoked\n");

let mut inner_guard = shared.inner.lock();
unsafe {
bindings::complete(&mut inner_guard.completion);
bindings::complete(Opaque::raw_get(&shared.completion));
}

// return non-zero value to avoid infinite re-try
Expand Down

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