From: Eric Dumazet edumazet@google.com
[ Upstream commit 61a0abaee2092eee69e44fe60336aa2f5b578938 ]
Commit 316580b69d0a ("u64_stats: provide u64_stats_t type") fixed possible load/store tearing on 64bit arches.
For instance the following C code
stats->nsecs += sched_clock() - start;
Could be rightfully implemented like this by a compiler, confusing concurrent readers a lot:
stats->nsecs += sched_clock(); // arbitrary delay stats->nsecs -= start;
Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20211026214133.3114279-4-eric.dumazet@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/filter.h | 10 +++++----- kernel/bpf/syscall.c | 18 ++++++++++++------ kernel/bpf/trampoline.c | 6 +++--- 3 files changed, 20 insertions(+), 14 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h index 1611dc9d44207..a9956b681f090 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -554,9 +554,9 @@ struct bpf_binary_header { };
struct bpf_prog_stats { - u64 cnt; - u64 nsecs; - u64 misses; + u64_stats_t cnt; + u64_stats_t nsecs; + u64_stats_t misses; struct u64_stats_sync syncp; } __aligned(2 * sizeof(u64));
@@ -618,8 +618,8 @@ static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog, ret = dfunc(ctx, prog->insnsi, prog->bpf_func); stats = this_cpu_ptr(prog->stats); flags = u64_stats_update_begin_irqsave(&stats->syncp); - stats->cnt++; - stats->nsecs += sched_clock() - start; + u64_stats_inc(&stats->cnt); + u64_stats_add(&stats->nsecs, sched_clock() - start); u64_stats_update_end_irqrestore(&stats->syncp, flags); } else { ret = dfunc(ctx, prog->insnsi, prog->bpf_func); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 53384622e8dac..42490c39dfbf5 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1824,8 +1824,14 @@ static int bpf_prog_release(struct inode *inode, struct file *filp) return 0; }
+struct bpf_prog_kstats { + u64 nsecs; + u64 cnt; + u64 misses; +}; + static void bpf_prog_get_stats(const struct bpf_prog *prog, - struct bpf_prog_stats *stats) + struct bpf_prog_kstats *stats) { u64 nsecs = 0, cnt = 0, misses = 0; int cpu; @@ -1838,9 +1844,9 @@ static void bpf_prog_get_stats(const struct bpf_prog *prog, st = per_cpu_ptr(prog->stats, cpu); do { start = u64_stats_fetch_begin_irq(&st->syncp); - tnsecs = st->nsecs; - tcnt = st->cnt; - tmisses = st->misses; + tnsecs = u64_stats_read(&st->nsecs); + tcnt = u64_stats_read(&st->cnt); + tmisses = u64_stats_read(&st->misses); } while (u64_stats_fetch_retry_irq(&st->syncp, start)); nsecs += tnsecs; cnt += tcnt; @@ -1856,7 +1862,7 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp) { const struct bpf_prog *prog = filp->private_data; char prog_tag[sizeof(prog->tag) * 2 + 1] = { }; - struct bpf_prog_stats stats; + struct bpf_prog_kstats stats;
bpf_prog_get_stats(prog, &stats); bin2hex(prog_tag, prog->tag, sizeof(prog->tag)); @@ -3595,7 +3601,7 @@ static int bpf_prog_get_info_by_fd(struct file *file, struct bpf_prog_info __user *uinfo = u64_to_user_ptr(attr->info.info); struct bpf_prog_info info; u32 info_len = attr->info.info_len; - struct bpf_prog_stats stats; + struct bpf_prog_kstats stats; char __user *uinsns; u32 ulen; int err; diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index d3a307a8c42b9..6933a9bfee637 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -544,7 +544,7 @@ static void notrace inc_misses_counter(struct bpf_prog *prog)
stats = this_cpu_ptr(prog->stats); u64_stats_update_begin(&stats->syncp); - stats->misses++; + u64_stats_inc(&stats->misses); u64_stats_update_end(&stats->syncp); }
@@ -589,8 +589,8 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
stats = this_cpu_ptr(prog->stats); flags = u64_stats_update_begin_irqsave(&stats->syncp); - stats->cnt++; - stats->nsecs += sched_clock() - start; + u64_stats_inc(&stats->cnt); + u64_stats_add(&stats->nsecs, sched_clock() - start); u64_stats_update_end_irqrestore(&stats->syncp, flags); } }