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From 34d968adeda2e06b057a13d14a88df5766b38eda Mon Sep 17 00:00:00 2001
From: Josh Matthews <josh@joshmatthews.net>
Date: Mon, 6 Jul 2020 14:37:42 -0400
Subject: [PATCH] Add signal handler to catch segfault in build script.
---
Cargo.lock | 11 +++++
webrender/Cargo.toml | 5 ++
webrender/backtrace.rs | 103 +++++++++++++++++++++++++++++++++++++++++
webrender/build.rs | 30 ++++++++++++
4 files changed, 149 insertions(+)
create mode 100644 webrender/backtrace.rs
diff --git a/Cargo.lock b/Cargo.lock
index afdd336ae..cf91162d5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1477,6 +1477,14 @@ dependencies = [
"libc 0.2.68 (registry+https://github.com/rust-lang/crates.io-index)",
]
+[[package]]
+name = "sig"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.68 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
[[package]]
name = "slab"
version = "0.4.2"
@@ -1750,6 +1758,7 @@ dependencies = [
name = "webrender"
version = "0.61.0"
dependencies = [
+ "backtrace 0.3.46 (registry+https://github.com/rust-lang/crates.io-index)",
"base64 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
"bincode 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
"bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1780,6 +1789,7 @@ dependencies = [
"ron 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
"serde 1.0.106 (registry+https://github.com/rust-lang/crates.io-index)",
"serde_json 1.0.51 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sig 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
"smallvec 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
"svg_fmt 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
"time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2178,6 +2188,7 @@ dependencies = [
"checksum servo-freetype-sys 4.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "2c4ccb6d0d32d277d3ef7dea86203d8210945eb7a45fba89dd445b3595dd0dfc"
"checksum sha-1 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f7d94d0bede923b3cea61f3f1ff57ff8cdfd77b400fb8f9998949e0cf04163df"
"checksum shared_library 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "5a9e7e0f2bfae24d8a5b5a66c5b257a83c7412304311512a0c054cd5e619da11"
+"checksum sig 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "6567e29578f9bfade6a5d94a32b9a4256348358d2a3f448cab0021f9a02614a2"
"checksum slab 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
"checksum smallvec 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)" = "f7b0758c52e15a8b5e3691eae6cc559f08eee9406e548a4477ba4e67770a82b6"
"checksum smallvec 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "05720e22615919e4734f6a99ceae50d00226c3c5aca406e102ebc33298214e0a"
diff --git a/webrender/Cargo.toml b/webrender/Cargo.toml
index dcf26d913..f7679da57 100644
--- a/webrender/Cargo.toml
+++ b/webrender/Cargo.toml
@@ -59,6 +59,11 @@ tracy-rs = { version = "0.1" }
mozangle = "0.3.1"
rand = "0.4"
+[target.'cfg(any(target_os = "macos", target_os = "linux"))'.build-dependencies]
+backtrace = "0.3"
+sig = "1.0"
+libc = "0.2"
+
[target.'cfg(any(target_os = "android", all(unix, not(target_os = "macos"))))'.dependencies]
freetype = { version = "0.4", default-features = false }
libc = "0.2"
diff --git a/webrender/backtrace.rs b/webrender/backtrace.rs
new file mode 100644
index 000000000..aa6bb6b32
--- /dev/null
+++ b/webrender/backtrace.rs
@@ -0,0 +1,103 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Similar to `println!("{:?}", Backtrace::new())`, but doesn’t allocate.
+//!
+//! Seems to fix some deadlocks: https://github.com/servo/servo/issues/24881
+//!
+//! FIXME: if/when a future version of the `backtrace` crate has
+//! https://github.com/rust-lang/backtrace-rs/pull/265, use that instead.
+
+use std::fmt::{self, Write};
+use backtrace::{BytesOrWideString, PrintFmt};
+
+#[inline(never)]
+pub(crate) fn print(w: &mut dyn std::io::Write) -> Result<(), std::io::Error> {
+ write!(w, "{:?}", Print {
+ print_fn_address: print as usize,
+ })
+}
+
+struct Print {
+ print_fn_address: usize,
+}
+
+impl fmt::Debug for Print {
+ fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ // Safety: we’re in a signal handler that is about to call `libc::_exit`.
+ // Potential data races from using `*_unsynchronized` functions are perhaps
+ // less bad than potential deadlocks?
+ unsafe {
+ let mut print_fn_frame = 0;
+ let mut frame_count = 0;
+ backtrace::trace_unsynchronized(|frame| {
+ let found = frame.symbol_address() as usize == self.print_fn_address;
+ if found {
+ print_fn_frame = frame_count;
+ }
+ frame_count += 1;
+ !found
+ });
+
+ let mode = PrintFmt::Short;
+ let mut p = print_path;
+ let mut f = backtrace::BacktraceFmt::new(fmt, mode, &mut p);
+ f.add_context()?;
+ let mut result = Ok(());
+ let mut frame_count = 0;
+ backtrace::trace_unsynchronized(|frame| {
+ let skip = frame_count < print_fn_frame;
+ frame_count += 1;
+ if skip {
+ return true
+ }
+
+ let mut frame_fmt = f.frame();
+ let mut any_symbol = false;
+ backtrace::resolve_frame_unsynchronized(frame, |symbol| {
+ any_symbol = true;
+ if let Err(e) = frame_fmt.symbol(frame, symbol) {
+ result = Err(e)
+ }
+ });
+ if !any_symbol {
+ if let Err(e) = frame_fmt.print_raw(frame.ip(), None, None, None) {
+ result = Err(e)
+ }
+ }
+ result.is_ok()
+ });
+ result?;
+ f.finish()
+ }
+ }
+}
+
+fn print_path(fmt: &mut fmt::Formatter, path: BytesOrWideString) -> fmt::Result {
+ match path {
+ BytesOrWideString::Bytes(mut bytes) => {
+ loop {
+ match std::str::from_utf8(bytes) {
+ Ok(s) => {
+ fmt.write_str(s)?;
+ break;
+ }
+ Err(err) => {
+ fmt.write_char(std::char::REPLACEMENT_CHARACTER)?;
+ match err.error_len() {
+ Some(len) => bytes = &bytes[err.valid_up_to() + len..],
+ None => break,
+ }
+ }
+ }
+ }
+ }
+ BytesOrWideString::Wide(wide) => {
+ for c in std::char::decode_utf16(wide.iter().cloned()) {
+ fmt.write_char(c.unwrap_or(std::char::REPLACEMENT_CHARACTER))?
+ }
+ }
+ }
+ Ok(())
+}
diff --git a/webrender/build.rs b/webrender/build.rs
index 3521d1342..36a7f17a8 100644
--- a/webrender/build.rs
+++ b/webrender/build.rs
@@ -244,7 +244,37 @@ fn write_optimized_shaders(shader_dir: &Path, shader_file: &mut File, out_dir: &
Ok(())
}
+#[cfg(any(target_os = "macos", target_os = "linux"))]
+mod backtrace;
+
+#[cfg(any(target_os = "macos", target_os = "linux"))]
+extern "C" fn handler(sig: i32) {
+ use std::sync::atomic;
+ static BEEN_HERE_BEFORE: atomic::AtomicBool = atomic::AtomicBool::new(false);
+ if !BEEN_HERE_BEFORE.swap(true, atomic::Ordering::SeqCst) {
+ let stdout = std::io::stdout();
+ let mut stdout = stdout.lock();
+ let _ = write!(&mut stdout, "Stack trace");
+ if let Some(name) = std::thread::current().name() {
+ let _ = write!(&mut stdout, " for thread \"{}\"", name);
+ }
+ let _ = write!(&mut stdout, "\n");
+ let _ = backtrace::print(&mut stdout);
+ }
+ unsafe {
+ libc::_exit(sig);
+ }
+}
+
fn main() -> Result<(), std::io::Error> {
+ #[cfg(any(target_os = "macos", target_os = "linux"))]
+ {
+ sig::signal!(sig::ffi::Sig::SEGV, handler); // handle segfaults
+ sig::signal!(sig::ffi::Sig::ILL, handler); // handle stack overflow and unsupported CPUs
+ sig::signal!(sig::ffi::Sig::IOT, handler); // handle double panics
+ sig::signal!(sig::ffi::Sig::BUS, handler); // handle invalid memory access
+ }
+
let out_dir = env::var("OUT_DIR").unwrap_or("out".to_owned());
let shaders_file_path = Path::new(&out_dir).join("shaders.rs");
--
2.39.2
|
