Re: [PATCH] linux/mem: atomically prefault hugepages in alloc_seg

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 20 May 2026 14:57:56 +0200
Michal Sieron <michal.sieron@nokia.com> wrote:

> In rare cases, when a secondary process calls rte_eal_init() it can
> cause a data race during page prefaulting in alloc_seg().
> 
> An atomic compare-exchange in a loop should eliminate the data race.
> 
> Signed-off-by: Michal Sieron <michal.sieron@nokia.com>
> ---

Build fails. Fix and resubmit.
Looks like you did this against older version of DPDK before stdatomic.

FAILED: [code=1] lib/librte_eal.a.p/eal_linux_eal_memalloc.c.o 
ccache clang -Ilib/librte_eal.a.p -Ilib -I../lib -Ilib/eal/common -I../lib/eal/common -I. -I.. -Iconfig -I../config -Ilib/eal/include -I../lib/eal/include -Ilib/eal/linux/include -I../lib/eal/linux/include -Ilib/eal/x86/include -I../lib/eal/x86/include -I../kernel/linux -Ilib/eal -I../lib/eal -Ilib/kvargs -I../lib/kvargs -Ilib/log -I../lib/log -Ilib/metrics -I../lib/metrics -Ilib/telemetry -I../lib/telemetry -Ilib/argparse -I../lib/argparse -Xclang -fcolor-diagnostics -fsanitize=undefined -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Werror -std=c11 -include rte_config.h -Wvla -Wcast-qual -Wcomma -Wdeprecated -Wformat -Wformat-nonliteral -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wold-style-definition -Wpointer-arith -Wshadow -Wsign-compare -Wstrict-prototypes -Wundef -Wwrite-strings -Wno-missing-field-initializers -D_GNU_SOURCE -fPIC -march=corei7 -mrtm -DALLOW_EXPERIMENTAL_API -DALLOW_INTERNAL_API '-DABI_VERSION="26.2"' -DRTE_EAL_PTHREAD_ATTR_SETAFFINITY_NP -DRTE_LOG_DEFAULT_LOGTYPE=lib.eal -DRTE_ANNOTATE_LOCKS -Wthread-safety -MD -MQ lib/librte_eal.a.p/eal_linux_eal_memalloc.c.o -MF lib/librte_eal.a.p/eal_linux_eal_memalloc.c.o.d -o lib/librte_eal.a.p/eal_linux_eal_memalloc.c.o -c ../lib/eal/linux/eal_memalloc.c
../lib/eal/linux/eal_memalloc.c:605:10: error: implicit declaration of function 'rte_atomic_compare_exchange_strong' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        while (!rte_atomic_compare_exchange_strong((volatile int *)addr, &snapshot, snapshot))
                ^
../lib/eal/linux/eal_memalloc.c:605:10: note: did you mean '__atomic_compare_exchange_n'?
../lib/eal/include/generic/rte_rwlock.h:189:6: note: '__atomic_compare_exchange_n' declared here
            rte_atomic_compare_exchange_weak_explicit(&rwl->cnt, &x, x + RTE_RWLOCK_WRITE,
            ^
../lib/eal/include/rte_stdatomic.h:151:2: note: expanded from macro 'rte_atomic_compare_exchange_weak_explicit'
        __atomic_compare_exchange_n(ptr, expected, desired, 1, \
        ^
1 error generated.