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[180.15.148.177]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21a9f217a60sm89161045ad.158.2025.01.15.20.43.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2025 20:43:10 -0800 (PST) From: FUJITA Tomonori To: linux-kernel@vger.kernel.org Cc: Boqun Feng , rust-for-linux@vger.kernel.org, netdev@vger.kernel.org, andrew@lunn.ch, hkallweit1@gmail.com, tmgross@umich.edu, ojeda@kernel.org, alex.gaynor@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, aliceryhl@google.com, anna-maria@linutronix.de, frederic@kernel.org, tglx@linutronix.de, arnd@arndb.de, jstultz@google.com, sboyd@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: [PATCH v8 6/7] rust: Add read_poll_timeout functions Date: Thu, 16 Jan 2025 13:40:58 +0900 Message-ID: <20250116044100.80679-7-fujita.tomonori@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250116044100.80679-1-fujita.tomonori@gmail.com> References: <20250116044100.80679-1-fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. core::panic::Location::file() doesn't provide a null-terminated string so add __might_sleep_precision() helper function, which takes a pointer to a string with its length. read_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] Co-developed-by: Boqun Feng Signed-off-by: Boqun Feng Signed-off-by: FUJITA Tomonori --- include/linux/kernel.h | 2 + kernel/sched/core.c | 28 +++++++++++--- rust/helpers/helpers.c | 1 + rust/helpers/kernel.c | 13 +++++++ rust/kernel/cpu.rs | 13 +++++++ rust/kernel/error.rs | 1 + rust/kernel/io.rs | 5 +++ rust/kernel/io/poll.rs | 84 ++++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 + 9 files changed, 144 insertions(+), 5 deletions(-) create mode 100644 rust/helpers/kernel.c create mode 100644 rust/kernel/cpu.rs create mode 100644 rust/kernel/io.rs create mode 100644 rust/kernel/io/poll.rs diff --git a/include/linux/kernel.h b/include/linux/kernel.h index be2e8c0a187e..086ee1dc447e 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -87,6 +87,7 @@ extern int dynamic_might_resched(void); #ifdef CONFIG_DEBUG_ATOMIC_SLEEP extern void __might_resched(const char *file, int line, unsigned int offse= ts); extern void __might_sleep(const char *file, int line); +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); =20 @@ -145,6 +146,7 @@ extern void __cant_migrate(const char *file, int line); static inline void __might_resched(const char *file, int line, unsigned int offsets) { } static inline void __might_sleep(const char *file, int line) { } +static inline void __might_sleep_precision(const char *file, int len, int = line) { } # define might_sleep() do { might_resched(); } while (0) # define cant_sleep() do { } while (0) # define cant_migrate() do { } while (0) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3e5a6bf587f9..d9ac66dc66d3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8670,7 +8670,10 @@ void __init sched_init(void) =20 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP =20 -void __might_sleep(const char *file, int line) +static void __might_resched_precision(const char *file, int len, + int line, unsigned int offsets); + +void __might_sleep_precision(const char *file, int len, int line) { unsigned int state =3D get_current_state(); /* @@ -8684,7 +8687,14 @@ void __might_sleep(const char *file, int line) (void *)current->task_state_change, (void *)current->task_state_change); =20 - __might_resched(file, line, 0); + __might_resched_precision(file, len, line, 0); +} + +void __might_sleep(const char *file, int line) +{ + long len =3D strlen(file); + + __might_sleep_precision(file, len, line); } EXPORT_SYMBOL(__might_sleep); =20 @@ -8709,7 +8719,8 @@ static inline bool resched_offsets_ok(unsigned int of= fsets) return nested =3D=3D offsets; } =20 -void __might_resched(const char *file, int line, unsigned int offsets) +static void __might_resched_precision(const char *file, int len, int line, + unsigned int offsets) { /* Ratelimiting timestamp: */ static unsigned long prev_jiffy; @@ -8732,8 +8743,8 @@ void __might_resched(const char *file, int line, unsi= gned int offsets) /* Save this before calling printk(), since that will clobber it: */ preempt_disable_ip =3D get_preempt_disable_ip(current); =20 - 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, nam= e: %s\n", in_atomic(), irqs_disabled(), current->non_block_count, current->pid, current->comm); @@ -8758,6 +8769,13 @@ void __might_resched(const char *file, int line, uns= igned int offsets) dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } + +void __might_resched(const char *file, int line, unsigned int offsets) +{ + long len =3D strlen(file); + + __might_resched_precision(file, len, line, offsets); +} EXPORT_SYMBOL(__might_resched); =20 void __cant_sleep(const char *file, int line, int preempt_offset) diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index d16aeda7a558..7ab71a6d4603 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -13,6 +13,7 @@ #include "build_bug.c" #include "cred.c" #include "err.c" +#include "kernel.c" #include "fs.c" #include "jump_label.c" #include "kunit.c" diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c new file mode 100644 index 000000000000..9dff28f4618e --- /dev/null +++ b/rust/helpers/kernel.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +void rust_helper_cpu_relax(void) +{ + cpu_relax(); +} + +void rust_helper___might_sleep_precision(const char *file, int len, int li= ne) +{ + __might_sleep_precision(file, len, line); +} diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs new file mode 100644 index 000000000000..eeeff4be84fa --- /dev/null +++ b/rust/kernel/cpu.rs @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Processor related primitives. +//! +//! C header: [`include/linux/processor.h`](srctree/include/linux/processo= r.h). + +/// Lower CPU power consumption or yield to a hyperthreaded twin processor. +/// +/// It also happens to serve as a compiler barrier. +pub fn cpu_relax() { + // SAFETY: FFI call. + unsafe { bindings::cpu_relax() } +} diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index f6ecf09cb65f..8858eb13b3df 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -64,6 +64,7 @@ macro_rules! declare_err { declare_err!(EPIPE, "Broken pipe."); declare_err!(EDOM, "Math argument out of domain of func."); declare_err!(ERANGE, "Math result not representable."); + declare_err!(ETIMEDOUT, "Connection timed out."); declare_err!(ERESTARTSYS, "Restart the system call."); declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal = and will be restarted."); declare_err!(ERESTARTNOHAND, "Restart if no handler."); diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs new file mode 100644 index 000000000000..033f3c4e4adf --- /dev/null +++ b/rust/kernel/io.rs @@ -0,0 +1,5 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Input and Output. + +pub mod poll; diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs new file mode 100644 index 000000000000..da8e975d8e50 --- /dev/null +++ b/rust/kernel/io/poll.rs @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! IO polling. +//! +//! C header: [`include/linux/iopoll.h`](srctree/include/linux/iopoll.h). + +use crate::{ + cpu::cpu_relax, + error::{code::*, Result}, + 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. +/// +/// ```rust +/// use kernel::io::poll::read_poll_timeout; +/// use kernel::time::Delta; +/// use kernel::sync::{SpinLock, new_spinlock}; +/// +/// let lock =3D KBox::pin_init(new_spinlock!(()), kernel::alloc::flags::G= FP_KERNEL)?; +/// let g =3D 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( + mut op: Op, + cond: Cond, + sleep_delta: Delta, + timeout_delta: Delta, +) -> Result +where + Op: FnMut() -> Result, + Cond: Fn(T) -> bool, +{ + let start =3D Instant::now(); + let sleep =3D !sleep_delta.is_zero(); + let timeout =3D !timeout_delta.is_zero(); + + might_sleep(Location::caller()); + + let val =3D loop { + let val =3D op()?; + if cond(val) { + // Unlike the C version, we immediately return. + // We know a condition is met so we don't need to check again. + return Ok(val); + } + if timeout && start.elapsed() > timeout_delta { + // Should we return Err(ETIMEDOUT) here instead of call op() a= gain + // without a sleep between? But we follow the C version. op() = could + // take some time so might be worth checking again. + break op()?; + } + if sleep { + fsleep(sleep_delta); + } + // fsleep() could be busy-wait loop so we always call cpu_relax(). + cpu_relax(); + }; + + if cond(val) { + Ok(val) + } else { + Err(ETIMEDOUT) + } +} + +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, + ) + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 545d1170ee63..c477701b2efa 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -35,6 +35,7 @@ pub mod block; #[doc(hidden)] pub mod build_assert; +pub mod cpu; pub mod cred; pub mod device; pub mod error; @@ -42,6 +43,7 @@ pub mod firmware; pub mod fs; pub mod init; +pub mod io; pub mod ioctl; pub mod jump_label; #[cfg(CONFIG_KUNIT)] --=20 2.43.0