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Message-ID: <2a31d520-454c-c837-ec17-12dbf879e6d3@intel.com> Date: Tue, 22 Feb 2022 11:27:28 +0100 From: Andrzej Hajda <andrzej.hajda@...el.com> To: Eric Dumazet <edumazet@...gle.com> CC: LKML <linux-kernel@...r.kernel.org>, <intel-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>, netdev <netdev@...r.kernel.org>, "Jani Nikula" <jani.nikula@...ux.intel.com>, Daniel Vetter <daniel@...ll.ch>, Lucas De Marchi <lucas.demarchi@...el.com>, Chris Wilson <chris.p.wilson@...el.com>, Dmitry Vyukov <dvyukov@...gle.com>, "Jakub Kicinski" <kuba@...nel.org> Subject: Re: [PATCH v3 05/11] lib/ref_tracker: __ref_tracker_dir_print improve printing On 22.02.2022 01:08, Eric Dumazet wrote: > On Mon, Feb 21, 2022 at 3:26 PM Andrzej Hajda <andrzej.hajda@...el.com> wrote: >> To improve readibility of ref_tracker printing following changes > readability > >> have been performed: >> - reports are printed per stack_handle - log is more compact, >> - added display name for ref_tracker_dir, >> - stack trace is printed indented, in the same printk call, >> - total number of references is printed every time, >> - print info about dropped references. >> >> Signed-off-by: Andrzej Hajda <andrzej.hajda@...el.com> >> --- >> include/linux/ref_tracker.h | 15 +++++-- >> lib/ref_tracker.c | 90 ++++++++++++++++++++++++++++++++----- >> 2 files changed, 91 insertions(+), 14 deletions(-) >> >> diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h >> index 3e9e9df2a41f5..a2cf1f6309adb 100644 >> --- a/include/linux/ref_tracker.h >> +++ b/include/linux/ref_tracker.h >> @@ -17,12 +17,19 @@ struct ref_tracker_dir { >> bool dead; >> struct list_head list; /* List of active trackers */ >> struct list_head quarantine; /* List of dead trackers */ >> + char name[32]; >> #endif >> }; >> >> #ifdef CONFIG_REF_TRACKER >> -static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir, >> - unsigned int quarantine_count) >> + >> +// Temporary allow two and three arguments, until consumers are converted >> +#define ref_tracker_dir_init(_d, _q, args...) _ref_tracker_dir_init(_d, _q, ##args, #_d) >> +#define _ref_tracker_dir_init(_d, _q, _n, ...) __ref_tracker_dir_init(_d, _q, _n) >> + >> +static inline void __ref_tracker_dir_init(struct ref_tracker_dir *dir, >> + unsigned int quarantine_count, >> + const char *name) >> { >> INIT_LIST_HEAD(&dir->list); >> INIT_LIST_HEAD(&dir->quarantine); >> @@ -31,6 +38,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir, >> dir->dead = false; >> refcount_set(&dir->untracked, 1); >> refcount_set(&dir->no_tracker, 1); >> + strlcpy(dir->name, name, sizeof(dir->name)); >> stack_depot_init(); >> } >> >> @@ -51,7 +59,8 @@ int ref_tracker_free(struct ref_tracker_dir *dir, >> #else /* CONFIG_REF_TRACKER */ >> >> static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir, >> - unsigned int quarantine_count) >> + unsigned int quarantine_count, >> + ...) >> { >> } >> >> diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c >> index 5e9f90bbf771b..ab1253fde244e 100644 >> --- a/lib/ref_tracker.c >> +++ b/lib/ref_tracker.c >> @@ -1,11 +1,16 @@ >> // SPDX-License-Identifier: GPL-2.0-or-later >> + >> +#define pr_fmt(fmt) "ref_tracker: " fmt >> + >> #include <linux/export.h> >> +#include <linux/list_sort.h> >> #include <linux/ref_tracker.h> >> #include <linux/slab.h> >> #include <linux/stacktrace.h> >> #include <linux/stackdepot.h> >> >> #define REF_TRACKER_STACK_ENTRIES 16 >> +#define STACK_BUF_SIZE 1024 >> >> struct ref_tracker { >> struct list_head head; /* anchor into dir->list or dir->quarantine */ >> @@ -14,24 +19,87 @@ struct ref_tracker { >> depot_stack_handle_t free_stack_handle; >> }; >> >> -void __ref_tracker_dir_print(struct ref_tracker_dir *dir, >> - unsigned int display_limit) >> +struct ref_tracker_dir_stats { >> + int total; >> + int count; >> + struct { >> + depot_stack_handle_t stack_handle; >> + unsigned int count; >> + } stacks[]; >> +}; >> + >> +static struct ref_tracker_dir_stats * >> +ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit) >> { >> + struct ref_tracker_dir_stats *stats; >> struct ref_tracker *tracker; >> - unsigned int i = 0; >> >> - lockdep_assert_held(&dir->lock); >> + stats = kmalloc(struct_size(stats, stacks, limit), >> + GFP_NOWAIT | __GFP_NOWARN); > I would be more comfortable if the allocation was done by the caller, > possibly using GFP_KERNEL and evenutally kvmalloc(), > instead of under dir->lock ? I though also about it, but decided to left this change to another patch as the change can be substantial and could open another discussion. I am not sure what you mean by 'caller' but it could be even external user of the API: 1. alloc data for ref_tracker_dir_stats. 2. take locks, if necessary. 3. gather stats (ref_tracker_get_stats) atomically. 4. release taken locks. 5. print stats. This way, allocation and printing would happen outside locks. > > >> + if (!stats) >> + return ERR_PTR(-ENOMEM); >> + stats->total = 0; >> + stats->count = 0; >> >> list_for_each_entry(tracker, &dir->list, head) { >> - if (i < display_limit) { >> - pr_err("leaked reference.\n"); >> - if (tracker->alloc_stack_handle) >> - stack_depot_print(tracker->alloc_stack_handle); >> - i++; >> - } else { >> - break; >> + depot_stack_handle_t stack = tracker->alloc_stack_handle; >> + int i; >> + >> + ++stats->total; >> + for (i = 0; i < stats->count; ++i) >> + if (stats->stacks[i].stack_handle == stack) >> + break; >> + if (i >= limit) >> + continue; >> + if (i >= stats->count) { >> + stats->stacks[i].stack_handle = stack; >> + stats->stacks[i].count = 0; >> + ++stats->count; >> } >> + ++stats->stacks[i].count; >> + } >> + >> + return stats; >> +} >> + >> +void __ref_tracker_dir_print(struct ref_tracker_dir *dir, >> + unsigned int display_limit) >> +{ >> + struct ref_tracker_dir_stats *stats; >> + unsigned int i = 0, skipped; >> + depot_stack_handle_t stack; >> + char *sbuf; >> + >> + lockdep_assert_held(&dir->lock); >> + >> + if (list_empty(&dir->list)) >> + return; >> + >> + stats = ref_tracker_get_stats(dir, display_limit); >> + if (IS_ERR(stats)) { >> + pr_err("%s@%pK: couldn't get stats, error %pe\n", >> + dir->name, dir, stats); >> + return; >> } >> + >> + sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN); > Same remark. These allocations are most probably going to happen from process > context, I think GFP_KERNEL is more robust. The problem is that in my scenario it can be called under spinlock, this is why I want almost everywhere non-sleeping allocations. > > This is debugging infra, it would be sad if we give up at this point, > after storing MB of traces :) My approach was to avoid allocations if the system is short on memory - better to keep it alive, and we still get the report, just without stacktraces, one can print full stats later (for example via sysfs, or trigger to dmesg) - big chances that the bug will be still there. If you think that is no-go, alternatives I see: - go back to GFP_ATOMIC, - print stack directly, without using stack_depot_snprint, - pre-allocate buffer. Regards Andrzej > >> + >> + for (i = 0, skipped = stats->total; i < stats->count; ++i) { >> + stack = stats->stacks[i].stack_handle; >> + if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4)) >> + sbuf[0] = 0; >> + pr_err("%s@%pK has %d/%d users at\n%s\n", dir->name, dir, >> + stats->stacks[i].count, stats->total, sbuf); >> + skipped -= stats->stacks[i].count; >> + } >> + >> + if (skipped) >> + pr_err("%s@%pK skipped reports about %d/%d users.\n", >> + dir->name, dir, skipped, stats->total); >> + >> + kfree(sbuf); >> + >> + kfree(stats); >> } >> EXPORT_SYMBOL(__ref_tracker_dir_print); >> >> -- >> 2.25.1 >>
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