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Merge #2769
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2769: Deadlock in emscripten dynamic calls r=Amanieu a=jcaesar

# Description

Attempting to run [an emscripten-built](#2498 (comment)) rust module lead me to a deadlock. I'm not quite sure what's wrong, but it looks to me like emscripten is calling itself through the host (No idea why. To catch exceptions?) and in the process, wasmer acquires a lock that is still held when calling back into the module. If the module tries that twice recursively, the simplest form of deadlock, a reentrancy deadlock is triggered.

The standard library doesn't have reentrant locks.
This cannot be solved by replacing the lock on `EmEnv.data` by an RwLock, because the code might also call `setTempRet0`, which does require a write lock. 
Maybe there is a way to get rid of the mutex entirely, but I do not see it.

The easy way out seems to be to clone the function (arcs), let go of the lock, and then do the call back into the module.

There are a few other instances of the same problematic pattern, but they call `memset` or `malloc`, which shouldn't call back into wasmer. I assume they are fine and left them alone, but have not done thorough testing.

# Review

- [x] Add a short description of the change to the CHANGELOG.md file



Co-authored-by: Julius Michaelis <glitter@liftm.de>
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@bors @jcaesar
bors[bot] and jcaesar committed Jan 27, 2022
2 parents 9d5e4ff + 77eebf3 commit 42059f7
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -9,6 +9,9 @@ Looking for changes that affect our C API? See the [C API Changelog](lib/c-api/C
## **[Unreleased]**
- [#2750](https://github.com/wasmerio/wasmer/pull/2750) Added Aarch64 support to Singlepass (both Linux and macOS).

### Fixed
- [#2769](https://github.com/wasmerio/wasmer/pull/2769) Deadlock in emscripten dynamic calls

## 2.1.1 - 2021/12/20

### Added
Expand Down
218 changes: 123 additions & 95 deletions lib/emscripten/src/emscripten_target.rs
View file
Expand Up @@ -140,8 +140,8 @@ pub fn _getnameinfo(
macro_rules! invoke {
($ctx: ident, $name:ident, $name_ref:ident, $( $arg:ident ),*) => {{
let sp = get_emscripten_data($ctx).stack_save_ref().expect("stack_save is None").call().expect("stack_save call failed");
let result = get_emscripten_data($ctx).$name_ref().expect(concat!("Dynamic call is None: ", stringify!($name))).call($($arg),*);
match result {
let call = get_emscripten_data($ctx).$name_ref().expect(concat!("Dynamic call is None: ", stringify!($name))).clone();
match call.call($($arg),*) {
Ok(v) => v,
Err(_e) => {
get_emscripten_data($ctx).stack_restore_ref().expect("stack_restore is None").call(sp).expect("stack_restore call failed");
Expand All @@ -156,8 +156,8 @@ macro_rules! invoke {
macro_rules! invoke_no_return {
($ctx: ident, $name:ident, $name_ref:ident, $( $arg:ident ),*) => {{
let sp = get_emscripten_data($ctx).stack_save_ref().expect("stack_save is None").call().expect("stack_save call failed");
let result = get_emscripten_data($ctx).$name_ref().expect(concat!("Dynamic call is None: ", stringify!($name))).call($($arg),*);
match result {
let call = get_emscripten_data($ctx).$name_ref().expect(concat!("Dynamic call is None: ", stringify!($name))).clone();
match call.call($($arg),*) {
Ok(v) => v,
Err(_e) => {
get_emscripten_data($ctx).stack_restore_ref().expect("stack_restore is None").call(sp).expect("stack_restore call failed");
Expand All @@ -168,6 +168,14 @@ macro_rules! invoke_no_return {
}
}};
}
// The invoke_j functions do not save the stack
macro_rules! invoke_no_stack_save {
($ctx: ident, $name:ident, $name_ref:ident, $( $arg:ident ),*) => {{
let call = get_emscripten_data($ctx).$name_ref().expect(concat!(stringify!($name), " is set to None")).clone();

call.call($($arg),*).unwrap()
}}
}

// Invoke functions
pub fn invoke_i(ctx: &EmEnv, index: i32) -> i32 {
Expand Down Expand Up @@ -604,52 +612,38 @@ pub fn invoke_iiijj(
}
pub fn invoke_j(ctx: &EmEnv, index: i32) -> i32 {
debug!("emscripten::invoke_j");
if let Some(dyn_call_j) = get_emscripten_data(ctx).dyn_call_j_ref() {
dyn_call_j.call(index).unwrap()
} else {
panic!("dyn_call_j is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_j, dyn_call_j_ref, index)
}
pub fn invoke_ji(ctx: &EmEnv, index: i32, a1: i32) -> i32 {
debug!("emscripten::invoke_ji");
if let Some(dyn_call_ji) = get_emscripten_data(ctx).dyn_call_ji_ref() {
dyn_call_ji.call(index, a1).unwrap()
} else {
panic!("dyn_call_ji is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_ji, dyn_call_ji_ref, index, a1)
}
pub fn invoke_jii(ctx: &EmEnv, index: i32, a1: i32, a2: i32) -> i32 {
debug!("emscripten::invoke_jii");
if let Some(dyn_call_jii) = get_emscripten_data(ctx).dyn_call_jii_ref() {
dyn_call_jii.call(index, a1, a2).unwrap()
} else {
panic!("dyn_call_jii is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_jii, dyn_call_jii_ref, index, a1, a2)
}

pub fn invoke_jij(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32) -> i32 {
debug!("emscripten::invoke_jij");
if let Some(dyn_call_jij) = get_emscripten_data(ctx).dyn_call_jij_ref() {
dyn_call_jij.call(index, a1, a2, a3).unwrap()
} else {
panic!("dyn_call_jij is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_jij, dyn_call_jij_ref, index, a1, a2, a3)
}
pub fn invoke_jjj(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32) -> i32 {
debug!("emscripten::invoke_jjj");
if let Some(dyn_call_jjj) = get_emscripten_data(ctx).dyn_call_jjj_ref() {
dyn_call_jjj.call(index, a1, a2, a3, a4).unwrap()
} else {
panic!("dyn_call_jjj is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_jjj, dyn_call_jjj_ref, index, a1, a2, a3, a4)
}
pub fn invoke_viiij(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32, a5: i32) {
debug!("emscripten::invoke_viiij");
if let Some(dyn_call_viiij) = get_emscripten_data(ctx).dyn_call_viiij_ref() {
dyn_call_viiij.call(index, a1, a2, a3, a4, a5).unwrap();
} else {
panic!("dyn_call_viiij is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viiij,
dyn_call_viiij_ref,
index,
a1,
a2,
a3,
a4,
a5
)
}
pub fn invoke_viiijiiii(
ctx: &EmEnv,
Expand All @@ -665,13 +659,21 @@ pub fn invoke_viiijiiii(
a9: i32,
) {
debug!("emscripten::invoke_viiijiiii");
if let Some(dyn_call_viiijiiii) = get_emscripten_data(ctx).dyn_call_viiijiiii_ref() {
dyn_call_viiijiiii
.call(index, a1, a2, a3, a4, a5, a6, a7, a8, a9)
.unwrap();
} else {
panic!("dyn_call_viiijiiii is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viiijiiii,
dyn_call_viiijiiii_ref,
index,
a1,
a2,
a3,
a4,
a5,
a6,
a7,
a8,
a9
)
}
pub fn invoke_viiijiiiiii(
ctx: &EmEnv,
Expand All @@ -689,29 +691,41 @@ pub fn invoke_viiijiiiiii(
a11: i32,
) {
debug!("emscripten::invoke_viiijiiiiii");
if let Some(dyn_call_viiijiiiiii) = get_emscripten_data(ctx).dyn_call_viiijiiiiii_ref() {
dyn_call_viiijiiiiii
.call(index, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11)
.unwrap();
} else {
panic!("dyn_call_viiijiiiiii is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viiijiiiiii,
dyn_call_viiijiiiiii_ref,
index,
a1,
a2,
a3,
a4,
a5,
a6,
a7,
a8,
a9,
a10,
a11
)
}
pub fn invoke_viij(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32) {
debug!("emscripten::invoke_viij");
if let Some(dyn_call_viij) = get_emscripten_data(ctx).dyn_call_viij_ref() {
dyn_call_viij.call(index, a1, a2, a3, a4).unwrap();
} else {
panic!("dyn_call_viij is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_viij, dyn_call_viij_ref, index, a1, a2, a3, a4)
}
pub fn invoke_viiji(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32, a5: i32) {
debug!("emscripten::invoke_viiji");
if let Some(dyn_call_viiji) = get_emscripten_data(ctx).dyn_call_viiji_ref() {
dyn_call_viiji.call(index, a1, a2, a3, a4, a5).unwrap();
} else {
panic!("dyn_call_viiji is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viiji,
dyn_call_viiji_ref,
index,
a1,
a2,
a3,
a4,
a5
)
}
pub fn invoke_viijiii(
ctx: &EmEnv,
Expand All @@ -725,29 +739,38 @@ pub fn invoke_viijiii(
a7: i32,
) {
debug!("emscripten::invoke_viijiii");
if let Some(dyn_call_viijiii) = get_emscripten_data(ctx).dyn_call_viijiii_ref() {
dyn_call_viijiii
.call(index, a1, a2, a3, a4, a5, a6, a7)
.unwrap();
} else {
panic!("dyn_call_viijiii is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viijiii,
dyn_call_viijiii_ref,
index,
a1,
a2,
a3,
a4,
a5,
a6,
a7
)
}
pub fn invoke_viijj(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32, a5: i32, a6: i32) {
debug!("emscripten::invoke_viijj");
if let Some(dyn_call_viijj) = get_emscripten_data(ctx).dyn_call_viijj_ref() {
dyn_call_viijj.call(index, a1, a2, a3, a4, a5, a6).unwrap();
} else {
panic!("dyn_call_viijj is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_viijj,
dyn_call_viijj_ref,
index,
a1,
a2,
a3,
a4,
a5,
a6
)
}
pub fn invoke_vj(ctx: &EmEnv, index: i32, a1: i32, a2: i32) {
debug!("emscripten::invoke_vj");
if let Some(dyn_call_vj) = get_emscripten_data(ctx).dyn_call_vj_ref() {
dyn_call_vj.call(index, a1, a2).unwrap();
} else {
panic!("dyn_call_vj is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_vj, dyn_call_vj_ref, index, a1, a2)
}
pub fn invoke_vjji(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32, a5: i32) {
debug!("emscripten::invoke_vjji");
Expand All @@ -765,19 +788,11 @@ pub fn invoke_vjji(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32,
}
pub fn invoke_vij(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32) {
debug!("emscripten::invoke_vij");
if let Some(dyn_call_vij) = get_emscripten_data(ctx).dyn_call_vij_ref() {
dyn_call_vij.call(index, a1, a2, a3).unwrap();
} else {
panic!("dyn_call_vij is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_vij, dyn_call_vij_ref, index, a1, a2, a3)
}
pub fn invoke_viji(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32) {
debug!("emscripten::invoke_viji");
if let Some(dyn_call_viji) = get_emscripten_data(ctx).dyn_call_viji_ref() {
dyn_call_viji.call(index, a1, a2, a3, a4).unwrap()
} else {
panic!("dyn_call_viji is set to None");
}
invoke_no_stack_save!(ctx, dyn_call_viji, dyn_call_viji_ref, index, a1, a2, a3, a4)
}
pub fn invoke_vijiii(
ctx: &EmEnv,
Expand All @@ -790,19 +805,32 @@ pub fn invoke_vijiii(
a6: i32,
) {
debug!("emscripten::invoke_vijiii");
if let Some(dyn_call_vijiii) = get_emscripten_data(ctx).dyn_call_vijiii_ref() {
dyn_call_vijiii.call(index, a1, a2, a3, a4, a5, a6).unwrap()
} else {
panic!("dyn_call_vijiii is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_vijiii,
dyn_call_vijiii_ref,
index,
a1,
a2,
a3,
a4,
a5,
a6
)
}
pub fn invoke_vijj(ctx: &EmEnv, index: i32, a1: i32, a2: i32, a3: i32, a4: i32, a5: i32) {
debug!("emscripten::invoke_vijj");
if let Some(dyn_call_vijj) = get_emscripten_data(ctx).dyn_call_vijj_ref() {
dyn_call_vijj.call(index, a1, a2, a3, a4, a5).unwrap()
} else {
panic!("dyn_call_vijj is set to None");
}
invoke_no_stack_save!(
ctx,
dyn_call_vijj,
dyn_call_vijj_ref,
index,
a1,
a2,
a3,
a4,
a5
)
}
pub fn invoke_vidd(ctx: &EmEnv, index: i32, a1: i32, a2: f64, a3: f64) {
debug!("emscripten::invoke_viid");
Expand Down

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