use_file: std::sync::Mutex, dropping all libpthread use.
#457
Conversation
briansmith
force-pushed
the
b/std-mutex
branch
3 times, most recently
from
9a4d42a
to
bc8d06e
Compare
It is only used in one configuration, so put it with the other stuff from that configuration.
| @@ -31,3 +31,65 @@ fn is_getrandom_available() -> bool { | |||
| true | |||
| } | |||
| } | |||
|
|
|||
| // Polls /dev/random to make sure it is ok to read from /dev/urandom. | |||
There was a problem hiding this comment.
As explained in the first commit, This code is only used on Linux/Android. With the other changes in this PR, DropGuard also became Linux/Android-specific. Instead of adding more #[cfg(...)] I just moved it all.
|
If we are adding a |
Unless/until we can use
No. Note that this PR effectively only uses libstd on targets for which we know libstd is already available. |
Well, actually, it is possible to use |
pthreads mutexes are not safe to move. While it is very unlikely that the mutex we create will ever be moved, we don't actively do anything to actively prevent it from being moved. (libstd, when it used/uses pthreads mutexes, would box them to prevent them from being moved.) Also, now on Linux and Android (and many other targets for which we don't use use_std), libstd uses futexes instead of pthreads mutexes. Thus using libstd's Mutex will be more efficient and avoid adding an often-otherwise-unnecessary libpthreads dependency on these targets. * Linux, Android: Futex [1]. * Haiku, Redox, NTO, AIX: pthreads [2]. * others: not using `use_file`. This will not affect our plans for *-*-linux-none, since we don't plan to use `use_file` for it. OnceLock This breaks 32-bit x86 QNX Neutrino, which doesn't have libstd because the target itself is abandoned [3]. the other QNX Neutrino targets didn't get libstd support until Rust 1.69, so this effectively raises the MSRV for them to 1.69. Otherwise, the MSRV increases to 1.63 for the above-mentioned targets, as that's when `Mutex::new()` became a `const fn`. I tried to use `Once` to avoid the MSRV increase but it doesn't support fallible initialization even in Nightly. `OnceLock` wasn't added until 1.70. On x86_64 Linux, this change removes all libpthreads dependencies: ```diff - pthread_mutex_lock - pthread_mutex_unlock ``` and adds these libstd dependencies: ```diff + std::panicking::panic_count::GLOBAL_PANIC_COUNT + std::panicking::panic_count::is_zero_slow_path + std::sys::sync::mutex::futex::Mutex::lock_contended + std::sys::sync::mutex::futex::Mutex::wake ``` as measured using `cargo asm`. [1] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L4-L10 [2] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L17-L20 [3] rust-random#453 (comment)
|
Closing this in favor of #458 based on @newpavlov's comment in the issue. |
use_file:
std::sync::Mutex, dropping all libpthread use.pthreads mutexes are not safe to move. While it is very unlikely that
the mutex we create will ever be moved, we don't actively do anything
to actively prevent it from being moved. (libstd, when it used/uses
pthreads mutexes, would box them to prevent them from being moved.)
Also, now on Linux and Android (and many other targets for which we
don't use use_std), libstd uses futexes instead of pthreads mutexes.
Thus using libstd's Mutex will be more efficient and avoid adding an
often-otherwise-unnecessary libpthreads dependency on these targets.
use_file.This will not affect our plans for --linux-none, since we don't
plan to use
use_filefor it. OnceLockThis breaks 32-bit x86 QNX Neutrino, which doesn't have libstd
because the target itself is abandoned [3]. the other QNX Neutrino
targets didn't get libstd support until Rust 1.69, so this
effectively raises the MSRV for them to 1.69.
Otherwise, the MSRV increases to 1.63 for the above-mentioned targets,
as that's when
Mutex::new()became aconst fn.I tried to use
Onceto avoid the MSRV increase but it doesn't supportfallible initialization even in Nightly.
OnceLockwasn't added until1.70.
On x86_64 Linux, this change removes all libpthreads dependencies:
and adds these libstd dependencies:
as measured using
cargo asm.[1] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L4-L10
[2] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L17-L20
[3] #453 (comment)