Commit 9a73fa37 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

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
parents 36a21d51 c3df5fb5

block/blk-cgroup.c

+8 −6
Original line number Diff line number Diff line
@@ -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);

		}

	}

}

kernel/cgroup/rstat.c

+11 −8
Original line number Diff line number Diff line
@@ -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);

}



/*