From aeb709c767aeca996e6011133e4f7bdb2a4af652 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Wed, 30 Sep 2026 09:59:20 +0000 Subject: selftests/bpf: Add a test for objects stuck in free_by_rcu_ttrace Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first free_bulk() starts RCU tasks trace GP and the rest of the elements are freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and waiting_for_gp_ttrace lists are empty. Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- include/vdso/helpers.h | 116 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 include/vdso/helpers.h (limited to 'include/vdso/helpers.h') diff --git a/include/vdso/helpers.h b/include/vdso/helpers.h new file mode 100644 index 000000000..65151b681 --- /dev/null +++ b/include/vdso/helpers.h @@ -0,0 +1,116 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __VDSO_HELPERS_H +#define __VDSO_HELPERS_H + +#ifndef __ASSEMBLER__ + +#include +#include +#include +#include + +static __always_inline bool vdso_is_timens_clock(const struct vdso_clock *vc) +{ + return IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS; +} + +static __always_inline u32 vdso_read_begin(const struct vdso_clock *vc) +{ + u32 seq; + + while (unlikely((seq = READ_ONCE(vc->seq)) & 1)) + cpu_relax(); + + smp_rmb(); + return seq; +} + +/* + * Variant of vdso_read_begin() to handle VDSO_CLOCKMODE_TIMENS. + * + * Time namespace enabled tasks have a special VVAR page installed which has + * vc->seq set to 1 and vc->clock_mode set to VDSO_CLOCKMODE_TIMENS. For non + * time namespace affected tasks this does not affect performance because if + * vc->seq is odd, i.e. a concurrent update is in progress the extra check for + * vc->clock_mode is just a few extra instructions while spin waiting for + * vc->seq to become even again. + */ +static __always_inline bool vdso_read_begin_timens(const struct vdso_clock *vc, u32 *seq) +{ + while (unlikely((*seq = READ_ONCE(vc->seq)) & 1)) { + if (vdso_is_timens_clock(vc)) + return true; + cpu_relax(); + } + smp_rmb(); + + return false; +} + +static __always_inline u32 vdso_read_retry(const struct vdso_clock *vc, + u32 start) +{ + u32 seq; + + smp_rmb(); + seq = READ_ONCE(vc->seq); + return unlikely(seq != start); +} + +static __always_inline void vdso_write_seq_begin(struct vdso_clock *vc) +{ + /* + * WRITE_ONCE() is required otherwise the compiler can validly tear + * updates to vc->seq and it is possible that the value seen by the + * reader is inconsistent. + */ + WRITE_ONCE(vc->seq, vc->seq + 1); +} + +static __always_inline void vdso_write_seq_end(struct vdso_clock *vc) +{ + /* + * WRITE_ONCE() is required otherwise the compiler can validly tear + * updates to vc->seq and it is possible that the value seen by the + * reader is inconsistent. + */ + WRITE_ONCE(vc->seq, vc->seq + 1); +} + +static __always_inline void vdso_write_begin_clock(struct vdso_clock *vc) +{ + vdso_write_seq_begin(vc); + /* Ensure the sequence invalidation is visible before data is modified */ + smp_wmb(); +} + +static __always_inline void vdso_write_end_clock(struct vdso_clock *vc) +{ + /* Ensure the data update is visible before the sequence is set valid again */ + smp_wmb(); + vdso_write_seq_end(vc); +} + +static __always_inline void vdso_write_begin(struct vdso_time_data *vd) +{ + struct vdso_clock *vc = vd->clock_data; + + vdso_write_seq_begin(&vc[CS_HRES_COARSE]); + vdso_write_seq_begin(&vc[CS_RAW]); + /* Ensure the sequence invalidation is visible before data is modified */ + smp_wmb(); +} + +static __always_inline void vdso_write_end(struct vdso_time_data *vd) +{ + struct vdso_clock *vc = vd->clock_data; + + /* Ensure the data update is visible before the sequence is set valid again */ + smp_wmb(); + vdso_write_seq_end(&vc[CS_HRES_COARSE]); + vdso_write_seq_end(&vc[CS_RAW]); +} + +#endif /* !__ASSEMBLER__ */ + +#endif /* __VDSO_HELPERS_H */ -- cgit v1.3.1