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Message-ID: <ZyvhDbNAhPTqIoVi@boqun-archlinux>
Date: Wed, 6 Nov 2024 13:35:09 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: anna-maria@...utronix.de, frederic@...nel.org, tglx@...utronix.de,
jstultz@...gle.com, sboyd@...nel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, rust-for-linux@...r.kernel.org,
andrew@...n.ch, hkallweit1@...il.com, tmgross@...ch.edu,
ojeda@...nel.org, alex.gaynor@...il.com, gary@...yguo.net,
bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
a.hindborg@...sung.com, aliceryhl@...gle.com, arnd@...db.de,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH v5 6/7] rust: Add read_poll_timeout functions
On Fri, Nov 01, 2024 at 10:01:20AM +0900, FUJITA Tomonori wrote:
> Add read_poll_timeout functions which poll periodically until a
> condition is met or a timeout is reached.
>
> C's read_poll_timeout (include/linux/iopoll.h) is a complicated macro
> and a simple wrapper for Rust doesn't work. So this implements the
> same functionality in Rust.
>
> The C version uses usleep_range() while the Rust version uses
> fsleep(), which uses the best sleep method so it works with spans that
> usleep_range() doesn't work nicely with.
>
> Unlike the C version, __might_sleep() is used instead of might_sleep()
> to show proper debug info; the file name and line
> number. might_resched() could be added to match what the C version
> does but this function works without it.
>
> The sleep_before_read argument isn't supported since there is no user
> for now. It's rarely used in the C version.
>
> For the proper debug info, readx_poll_timeout() and __might_sleep()
> are implemented as a macro. We could implement them as a normal
> function if there is a clean way to get a null-terminated string
> without allocation from core::panic::Location::file().
>
So printk() actually support printing a string with a precison value,
that is: a format string "%.*s" would take two inputs, one for the length
and the other for the pointer to the string, for example you can do:
char *msg = "hello";
printk("%.*s\n", 5, msg);
This is similar to printf() in glibc [1].
If we add another __might_sleep_precision() which accepts a file name
length:
void __might_sleep_precision(const char *file, int len, int line)
then we don't need to use macro here, I've attached a diff based
on your whole patchset, and it seems working.
Cc printk folks to if they know any limitation on using precision.
Regards,
Boqun
[1]: https://www.gnu.org/software/libc/manual/html_node/Output-Conversion-Syntax.html#Output-Conversion-Syntax
> readx_poll_timeout() can only be used in a nonatomic context. This
> requirement is not checked by these abstractions, but it is
> intended that klint [1] or a similar tool will be used to check it
> in the future.
>
> Link: https://rust-for-linux.com/klint [1]
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
> ---
--------------------------------------------->8
diff --git a/drivers/net/phy/qt2025.rs b/drivers/net/phy/qt2025.rs
index dabb772c468f..4d368ce80db6 100644
--- a/drivers/net/phy/qt2025.rs
+++ b/drivers/net/phy/qt2025.rs
@@ -18,7 +18,7 @@
Driver,
};
use kernel::prelude::*;
-use kernel::readx_poll_timeout;
+use kernel::read_poll_timeout;
use kernel::sizes::{SZ_16K, SZ_8K};
use kernel::time::Delta;
@@ -95,7 +95,7 @@ fn probe(dev: &mut phy::Device) -> Result<()> {
// The micro-controller will start running from SRAM.
dev.write(C45::new(Mmd::PCS, 0xe854), 0x0040)?;
- readx_poll_timeout!(
+ read_poll_timeout(
|| dev.read(C45::new(Mmd::PCS, 0xd7fd)),
|val| val != 0x00 && val != 0x10,
Delta::from_millis(50),
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index be2e8c0a187e..b405b0d19bac 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -87,6 +87,8 @@ extern int dynamic_might_resched(void);
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
extern void __might_resched(const char *file, int line, unsigned int offsets);
extern void __might_sleep(const char *file, int line);
+extern void __might_resched_precision(const char *file, int len, int line, unsigned int offsets);
+extern void __might_sleep_precision(const char *file, int len, int line);
extern void __cant_sleep(const char *file, int line, int preempt_offset);
extern void __cant_migrate(const char *file, int line);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 43e453ab7e20..f872aa18eaf0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8543,7 +8543,7 @@ void __init sched_init(void)
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-void __might_sleep(const char *file, int line)
+void __might_sleep_precision(const char *file, int len, int line)
{
unsigned int state = get_current_state();
/*
@@ -8557,7 +8557,14 @@ void __might_sleep(const char *file, int line)
(void *)current->task_state_change,
(void *)current->task_state_change);
- __might_resched(file, line, 0);
+ __might_resched_precision(file, len, line, 0);
+}
+
+void __might_sleep(const char *file, int line)
+{
+ long len = strlen(file);
+
+ __might_sleep_precision(file, len, line);
}
EXPORT_SYMBOL(__might_sleep);
@@ -8582,7 +8589,7 @@ static inline bool resched_offsets_ok(unsigned int offsets)
return nested == offsets;
}
-void __might_resched(const char *file, int line, unsigned int offsets)
+void __might_resched_precision(const char *file, int len, int line, unsigned int offsets)
{
/* Ratelimiting timestamp: */
static unsigned long prev_jiffy;
@@ -8605,8 +8612,8 @@ void __might_resched(const char *file, int line, unsigned int offsets)
/* Save this before calling printk(), since that will clobber it: */
preempt_disable_ip = get_preempt_disable_ip(current);
- pr_err("BUG: sleeping function called from invalid context at %s:%d\n",
- file, line);
+ pr_err("BUG: sleeping function called from invalid context at %.*s:%d\n",
+ len, file, line);
pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
in_atomic(), irqs_disabled(), current->non_block_count,
current->pid, current->comm);
@@ -8631,6 +8638,13 @@ void __might_resched(const char *file, int line, unsigned int offsets)
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
+
+void __might_resched(const char *file, int line, unsigned int offsets)
+{
+ long len = strlen(file);
+
+ __might_resched_precision(file, len, line, offsets);
+}
EXPORT_SYMBOL(__might_resched);
void __cant_sleep(const char *file, int line, int preempt_offset)
diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c
index da847059260b..9dff28f4618e 100644
--- a/rust/helpers/kernel.c
+++ b/rust/helpers/kernel.c
@@ -7,7 +7,7 @@ void rust_helper_cpu_relax(void)
cpu_relax();
}
-void rust_helper___might_sleep(const char *file, int line)
+void rust_helper___might_sleep_precision(const char *file, int len, int line)
{
- __might_sleep(file, line);
+ __might_sleep_precision(file, len, line);
}
diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs
index a8caa08f86f2..d7e5be162b6e 100644
--- a/rust/kernel/io/poll.rs
+++ b/rust/kernel/io/poll.rs
@@ -10,10 +10,25 @@
time::{delay::fsleep, Delta, Instant},
};
+use core::panic::Location;
+
/// Polls periodically until a condition is met or a timeout is reached.
///
/// Public but hidden since it should only be used from public macros.
-#[doc(hidden)]
+///
+/// ```rust
+/// use kernel::io::poll::read_poll_timeout;
+/// use kernel::time::Delta;
+/// use kernel::sync::{SpinLock, new_spinlock};
+///
+/// let lock = KBox::pin_init(new_spinlock!(()), kernel::alloc::flags::GFP_KERNEL)?;
+/// let g = lock.lock();
+/// read_poll_timeout(|| Ok(()), |()| true, Delta::from_micros(42), Delta::from_micros(42));
+/// drop(g);
+///
+/// # Ok::<(), Error>(())
+/// ```
+#[track_caller]
pub fn read_poll_timeout<Op, Cond, T: Copy>(
mut op: Op,
cond: Cond,
@@ -28,6 +43,8 @@ pub fn read_poll_timeout<Op, Cond, T: Copy>(
let sleep = !sleep_delta.is_zero();
let timeout = !timeout_delta.is_zero();
+ might_sleep(Location::caller());
+
let val = loop {
let val = op()?;
if cond(val) {
@@ -55,41 +72,13 @@ pub fn read_poll_timeout<Op, Cond, T: Copy>(
}
}
-/// Print debug information if it's called inside atomic sections.
-///
-/// Equivalent to the kernel's [`__might_sleep`].
-#[macro_export]
-macro_rules! __might_sleep {
- () => {
- #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)]
- // SAFETY: FFI call.
- unsafe {
- $crate::bindings::__might_sleep(
- c_str!(::core::file!()).as_char_ptr(),
- ::core::line!() as i32,
- )
- }
- };
-}
-
-/// Polls periodically until a condition is met or a timeout is reached.
-///
-/// `op` is called repeatedly until `cond` returns `true` or the timeout is
-/// reached. The return value of `op` is passed to `cond`.
-///
-/// `sleep_delta` is the duration to sleep between calls to `op`.
-/// If `sleep_delta` is less than one microsecond, the function will busy-wait.
-///
-/// `timeout_delta` is the maximum time to wait for `cond` to return `true`.
-///
-/// This macro can only be used in a nonatomic context.
-#[macro_export]
-macro_rules! readx_poll_timeout {
- ($op:expr, $cond:expr, $sleep_delta:expr, $timeout_delta:expr) => {{
- if !$sleep_delta.is_zero() {
- $crate::__might_sleep!();
- }
-
- $crate::io::poll::read_poll_timeout($op, $cond, $sleep_delta, $timeout_delta)
- }};
+fn might_sleep(loc: &Location<'_>) {
+ // SAFETY: FFI call.
+ unsafe {
+ crate::bindings::__might_sleep_precision(
+ loc.file().as_ptr().cast(),
+ loc.file().len() as i32,
+ loc.line() as i32,
+ )
+ }
}
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