kernel/linux.git/fs/select.c, branch v7.0-rc7

Convert more 'alloc_obj' cases to default GFP_KERNEL arguments

2026-02-22T04:03:00+00:00

This converts some of the visually simpler cases that have been split over multiple lines. I only did the ones that are easy to verify the resulting diff by having just that final GFP_KERNEL argument on the next line. Somebody should probably do a proper coccinelle script for this, but for me the trivial script actually resulted in an assertion failure in the middle of the script. I probably had made it a bit _too_ trivial. So after fighting that far a while I decided to just do some of the syntactically simpler cases with variations of the previous 'sed' scripts. The more syntactically complex multi-line cases would mostly really want whitespace cleanup anyway. Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

select: store end_time as timespec64 in restart block

2025-12-24T13:01:57+00:00

Storing the end time seconds as 'unsigned long' can lead to truncation on 32-bit architectures if assigned from the 64-bit timespec64::tv_sec. As the select() core uses timespec64 consistently, also use that in the restart block. This also allows the simplification of the accessors. Signed-off-by: Thomas Weißschuh Link: https://patch.msgid.link/20251223-restart-block-expiration-v2-1-8e33e5df7359@linutronix.de Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

select: Convert to scoped user access

2025-11-04T07:28:34+00:00

Replace the open coded implementation with the scoped user access guard. No functional change intended. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Link: https://patch.msgid.link/20251027083745.862419776@linutronix.de

fs: annotate suspected data race between poll_schedule_timeout() and pollwake()

2025-06-23T10:36:51+00:00

When running almost any select()/poll() workload intense enough, KCSAN is likely to report data races around using 'triggered' flag of 'struct poll_wqueues'. For example, running 'find /' on a tty console may trigger the following: BUG: KCSAN: data-race in poll_schedule_timeout / pollwake write to 0xffffc900030cfb90 of 4 bytes by task 97 on cpu 5: pollwake+0xd1/0x130 __wake_up_common_lock+0x7f/0xd0 n_tty_receive_buf_common+0x776/0xc30 n_tty_receive_buf2+0x3d/0x60 tty_ldisc_receive_buf+0x6b/0x100 tty_port_default_receive_buf+0x63/0xa0 flush_to_ldisc+0x169/0x3c0 process_scheduled_works+0x6fe/0xf40 worker_thread+0x53b/0x7b0 kthread+0x4f8/0x590 ret_from_fork+0x28c/0x450 ret_from_fork_asm+0x1a/0x30 read to 0xffffc900030cfb90 of 4 bytes by task 5802 on cpu 4: poll_schedule_timeout+0x96/0x160 do_sys_poll+0x966/0xb30 __se_sys_ppoll+0x1c3/0x210 __x64_sys_ppoll+0x71/0x90 x64_sys_call+0x3079/0x32b0 do_syscall_64+0xfa/0x3b0 entry_SYSCALL_64_after_hwframe+0x77/0x7f According to Jan, "there's no practical issue here because it is hard to imagine how the compiler could compile the above code using some intermediate values stored into 'triggered' or multiple fetches from 'triggered'". Nevertheless, silence KCSAN by using WRITE_ONCE() in __pollwake() and READ_ONCE() in poll_schedule_timeout(), respectively. Link: https://lore.kernel.org/linux-fsdevel/bwx72orsztfjx6aoftzzkl7wle3hi4syvusuwc7x36nw6t235e@bjwrosehblty Signed-off-by: Dmitry Antipov Link: https://lore.kernel.org/20250620063059.1800689-1-dmantipov@yandex.ru Acked-by: Marco Elver Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

select: core_sys_select add unlikely branch hint on return path

2025-04-21T08:27:58+00:00

Adding an unlikely() hint on the n < 0 comparison return path improves run-time performance of the select() system call, the negative value of n is very uncommon in normal select usage. Benchmarking on an Debian based Intel(R) Core(TM) Ultra 9 285K with a 6.15-rc1 kernel built with 14.2.0 using a select of 1000 file descriptors with zero timeout shows a consistent call reduction from 258 ns down to 254 ns, which is a ~1.5% performance improvement. Results based on running 25 tests with turbo disabled (to reduce clock freq turbo changes), with 30 second run per test and comparing the number of select() calls per second. The % standard deviation of the 25 tests was 0.24%, so results are reliable. Signed-off-by: Colin Ian King Link: https://lore.kernel.org/20250414092426.53529-1-colin.i.king@gmail.com Signed-off-by: Christian Brauner

select: do_pollfd: add unlikely branch hint return path

2025-04-11T13:56:54+00:00

Adding an unlikely() hint on the fd < 0 comparison return path improves run-time performance of the poll() system call. gcov based coverage analysis based on running stress-ng and a kernel build shows that this path return path is highly unlikely. Benchmarking on an Debian based Intel(R) Core(TM) Ultra 9 285K with a 6.15-rc1 kernel and a poll of 1024 file descriptors with zero timeout shows an call reduction from 32818 ns down to 32635 ns, which is a ~0.5% performance improvement. Results based on running 25 tests with turbo disabled (to reduce clock freq turbo changes), with 30 second run per test and comparing the number of poll() calls per second. The % standard deviation of the 25 tests was 0.08%, so results are reliable. Signed-off-by: Colin Ian King Link: https://lore.kernel.org/20250409155510.577490-1-colin.i.king@gmail.com Signed-off-by: Christian Brauner

select: Fix unbalanced user_access_end()

2025-01-13T15:24:16+00:00

While working on implementing user access validation on powerpc I got the following warnings on a pmac32_defconfig build: CC fs/select.o fs/select.o: warning: objtool: sys_pselect6+0x1bc: redundant UACCESS disable fs/select.o: warning: objtool: sys_pselect6_time32+0x1bc: redundant UACCESS disable On powerpc/32s, user_read_access_begin/end() are no-ops, but the failure path has a user_access_end() instead of user_read_access_end() which means an access end without any prior access begin. Replace that user_access_end() by user_read_access_end(). Fixes: 7e71609f64ec ("pselect6() and friends: take handling the combined 6th/7th args into helper") Signed-off-by: Christophe Leroy Link: https://lore.kernel.org/r/a7139e28d767a13e667ee3c79599a8047222ef36.1736751221.git.christophe.leroy@csgroup.eu Signed-off-by: Christian Brauner

do_pollfd(): convert to CLASS(fd)

2024-11-03T06:28:07+00:00

lift setting ->revents into the caller, so that failure exits (including the early one) would be plain returns. We need the scope of our struct fd to end before the store to ->revents, since that's shared with the failure exits prior to the point where we can do fdget(). Reviewed-by: Christian Brauner Signed-off-by: Al Viro

convert do_select()

2024-11-03T06:28:07+00:00

take the logics from fdget() to fdput() into an inlined helper - with existing wait_key_set() subsumed into that. Reviewed-by: Christian Brauner Signed-off-by: Al Viro