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Merge branch 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

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Pull cgroup fix from Tejun Heo:
 "One commit to fix a possible A-A deadlock around u64_stats_sync on
  32bit machines caused by updating it without disabling IRQ when it may
  be read from IRQ context"

* 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: rstat: fix A-A deadlock on 32bit around u64_stats_sync
This commit is contained in:
Linus Torvalds 2021-08-09 16:47:36 -07:00
commit 9a73fa375d
2 changed files with 19 additions and 14 deletions
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14
block/blk-cgroup.c
View File

@ -790,6 +790,7 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
struct blkcg_gq *parent = blkg->parent;
struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu);
struct blkg_iostat cur, delta;
unsigned long flags;
unsigned int seq;
/* fetch the current per-cpu values */
@ -799,21 +800,21 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
} while (u64_stats_fetch_retry(&bisc->sync, seq));
/* propagate percpu delta to global */
u64_stats_update_begin(&blkg->iostat.sync);
flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
blkg_iostat_set(&delta, &cur);
blkg_iostat_sub(&delta, &bisc->last);
blkg_iostat_add(&blkg->iostat.cur, &delta);
blkg_iostat_add(&bisc->last, &delta);
u64_stats_update_end(&blkg->iostat.sync);
u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
/* propagate global delta to parent (unless that's root) */
if (parent && parent->parent) {
u64_stats_update_begin(&parent->iostat.sync);
flags = u64_stats_update_begin_irqsave(&parent->iostat.sync);
blkg_iostat_set(&delta, &blkg->iostat.cur);
blkg_iostat_sub(&delta, &blkg->iostat.last);
blkg_iostat_add(&parent->iostat.cur, &delta);
blkg_iostat_add(&blkg->iostat.last, &delta);
u64_stats_update_end(&parent->iostat.sync);
u64_stats_update_end_irqrestore(&parent->iostat.sync, flags);
}
}
@ -848,6 +849,7 @@ static void blkcg_fill_root_iostats(void)
memset(&tmp, 0, sizeof(tmp));
for_each_possible_cpu(cpu) {
struct disk_stats *cpu_dkstats;
unsigned long flags;
cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
tmp.ios[BLKG_IOSTAT_READ] +=
@ -864,9 +866,9 @@ static void blkcg_fill_root_iostats(void)
tmp.bytes[BLKG_IOSTAT_DISCARD] +=
cpu_dkstats->sectors[STAT_DISCARD] << 9;
u64_stats_update_begin(&blkg->iostat.sync);
flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
blkg_iostat_set(&blkg->iostat.cur, &tmp);
u64_stats_update_end(&blkg->iostat.sync);
u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
}
}
}

19
kernel/cgroup/rstat.c
View File

@ -347,19 +347,20 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
}
static struct cgroup_rstat_cpu *
cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp)
cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
{
struct cgroup_rstat_cpu *rstatc;
rstatc = get_cpu_ptr(cgrp->rstat_cpu);
u64_stats_update_begin(&rstatc->bsync);
*flags = u64_stats_update_begin_irqsave(&rstatc->bsync);
return rstatc;
}
static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
struct cgroup_rstat_cpu *rstatc)
struct cgroup_rstat_cpu *rstatc,
unsigned long flags)
{
u64_stats_update_end(&rstatc->bsync);
u64_stats_update_end_irqrestore(&rstatc->bsync, flags);
cgroup_rstat_updated(cgrp, smp_processor_id());
put_cpu_ptr(rstatc);
}
@ -367,18 +368,20 @@ static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
{
struct cgroup_rstat_cpu *rstatc;
unsigned long flags;
rstatc = cgroup_base_stat_cputime_account_begin(cgrp);
rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
cgroup_base_stat_cputime_account_end(cgrp, rstatc);
cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
}
void __cgroup_account_cputime_field(struct cgroup *cgrp,
enum cpu_usage_stat index, u64 delta_exec)
{
struct cgroup_rstat_cpu *rstatc;
unsigned long flags;
rstatc = cgroup_base_stat_cputime_account_begin(cgrp);
rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
switch (index) {
case CPUTIME_USER:
@ -394,7 +397,7 @@ void __cgroup_account_cputime_field(struct cgroup *cgrp,
break;
}
cgroup_base_stat_cputime_account_end(cgrp, rstatc);
cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
}
/*