# [PATCH 0/2] read-cache: two small leak fixes 11 messages from 2024-09-30 to 2024-10-02. Participants: Derrick Stolee via GitGitGadget, Patrick Steinhardt, Derrick Stolee. Thread: https://gitlist.dev/t/62217 ## Derrick Stolee via GitGitGadget, 2024-09-30 11:40 Subject: [PATCH 0/2] read-cache: two small leak fixes Message-ID: URL: https://gitlist.dev/e/pull.1801.git.1727696424.gitgitgadget%40gmail.com ``` I found these two small memory leaks while investigating things involving the index. I thought they were small enough to send independently. I initially wrote this as two patches because the second patch was more involved to work around the "cleanup" label, and my branch was based on 2.46.1. This code has changed recently due to d1c53f6703 (read-cache: fix leaking hashfile when writing index fails, 2024-08-14), so now the second patch is simpler and these could probably be merged into one. Thanks, -Stolee Derrick Stolee (2): read-cache: free threaded memory pool read-cache: free hash context in do_write_index() read-cache.c | 2 ++ 1 file changed, 2 insertions(+) base-commit: 6258f68c3c1092c901337895c864073dcdea9213 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1801%2Fderrickstolee%2Fleaks-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1801/derrickstolee/leaks-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/1801 -- gitgitgadget ``` ## Derrick Stolee via GitGitGadget, 2024-09-30 11:40 Subject: [PATCH 1/2] read-cache: free threaded memory pool Message-ID: <9a45b15ea4b9864cd3cff066ecd9281c4539d5f7.1727696424.git.gitgitgadget@gmail.com> URL: https://gitlist.dev/e/9a45b15ea4b9864cd3cff066ecd9281c4539d5f7.1727696424.git.gitgitgadget%40gmail.com In-Reply-To: ``` From: Derrick Stolee In load_cache_entries_threaded(), each thread is allocated its own memory pool. This pool needs to be cleaned up while closing the threads down, or it will be leaked. Signed-off-by: Derrick Stolee --- read-cache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/read-cache.c b/read-cache.c index 764fdfec465..3c078afadbc 100644 --- a/read-cache.c +++ b/read-cache.c @@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con if (err) die(_("unable to join load_cache_entries thread: %s"), strerror(err)); mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool); + free(p->ce_mem_pool); consumed += p->consumed; } -- gitgitgadget ``` ## Derrick Stolee via GitGitGadget, 2024-09-30 11:40 Subject: [PATCH 2/2] read-cache: free hash context in do_write_index() Message-ID: URL: https://gitlist.dev/e/b6fe5b3ef7e5f4ac8cc339685d92e3ac39fcb456.1727696424.git.gitgitgadget%40gmail.com In-Reply-To: ``` From: Derrick Stolee While writing an index, a 'git_hash_ctx' is allocated for hashing the file contents. This should be freed as the method exits. Signed-off-by: Derrick Stolee --- read-cache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/read-cache.c b/read-cache.c index 3c078afadbc..51845c2e611 100644 --- a/read-cache.c +++ b/read-cache.c @@ -3126,6 +3126,7 @@ out: free_hashfile(f); strbuf_release(&sb); free(ieot); + free(eoie_c); return ret; } -- gitgitgadget ``` ## Patrick Steinhardt, 2024-09-30 12:32 Subject: Re: [PATCH 2/2] read-cache: free hash context in do_write_index() Message-ID: URL: https://gitlist.dev/e/ZvqaRIY1OzOIh1bc%40pks.im In-Reply-To: ``` On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee > > While writing an index, a 'git_hash_ctx' is allocated for hashing the > file contents. This should be freed as the method exits. > > Signed-off-by: Derrick Stolee > --- > read-cache.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/read-cache.c b/read-cache.c > index 3c078afadbc..51845c2e611 100644 > --- a/read-cache.c > +++ b/read-cache.c > @@ -3126,6 +3126,7 @@ out: > free_hashfile(f); > strbuf_release(&sb); > free(ieot); > + free(eoie_c); > return ret; > } Yup, this one looks correct. I've sent out an equivalent patch via [1] a couple hours ago. Patrick [1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/ ``` ## Patrick Steinhardt, 2024-09-30 12:32 Subject: Re: [PATCH 1/2] read-cache: free threaded memory pool Message-ID: URL: https://gitlist.dev/e/ZvqaTqegJxow1x-b%40pks.im In-Reply-To: <9a45b15ea4b9864cd3cff066ecd9281c4539d5f7.1727696424.git.gitgitgadget@gmail.com> ``` On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee > > In load_cache_entries_threaded(), each thread is allocated its own s/allocated/allocating/ > memory pool. This pool needs to be cleaned up while closing the threads > down, or it will be leaked. > > Signed-off-by: Derrick Stolee > --- > read-cache.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/read-cache.c b/read-cache.c > index 764fdfec465..3c078afadbc 100644 > --- a/read-cache.c > +++ b/read-cache.c > @@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con > if (err) > die(_("unable to join load_cache_entries thread: %s"), strerror(err)); > mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool); > + free(p->ce_mem_pool); > consumed += p->consumed; > } Okay. We move over the contents of the pool, but forgot to free the pool itself. As far as I can see the pool is always allocated and only used in two functions, both of which assume that it is allocated. So I wonder why it is allocated in the first place instead of making it a direct member of `struct load_cache_entries_thread_data`. Patrick ``` ## Derrick Stolee, 2024-10-01 10:01 Subject: Re: [PATCH 2/2] read-cache: free hash context in do_write_index() Message-ID: <0f257003-5a8d-4eca-987d-517d9754f1fd@gmail.com> URL: https://gitlist.dev/e/0f257003-5a8d-4eca-987d-517d9754f1fd%40gmail.com In-Reply-To: ``` On 9/30/24 8:32 AM, Patrick Steinhardt wrote: > On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote: >> From: Derrick Stolee >> diff --git a/read-cache.c b/read-cache.c >> index 3c078afadbc..51845c2e611 100644 >> --- a/read-cache.c >> +++ b/read-cache.c >> @@ -3126,6 +3126,7 @@ out: >> free_hashfile(f); >> strbuf_release(&sb); >> free(ieot); >> + free(eoie_c); >> return ret; >> } > > Yup, this one looks correct. I've sent out an equivalent patch via [1] a > couple hours ago. > > Patrick > > [1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/ Sorry for the collision. I had checked when prepping the GGG PR on Friday but forgot to check again before submitting. Your patch is better in substance and context. Thanks, -Stolee ``` ## Patrick Steinhardt, 2024-10-01 10:16 Subject: Re: [PATCH 2/2] read-cache: free hash context in do_write_index() Message-ID: URL: https://gitlist.dev/e/ZvvL6bdcV-05tFYY%40pks.im In-Reply-To: <0f257003-5a8d-4eca-987d-517d9754f1fd@gmail.com> ``` On Tue, Oct 01, 2024 at 06:01:06AM -0400, Derrick Stolee wrote: > On 9/30/24 8:32 AM, Patrick Steinhardt wrote: > > On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote: > > > From: Derrick Stolee > > > > diff --git a/read-cache.c b/read-cache.c > > > index 3c078afadbc..51845c2e611 100644 > > > --- a/read-cache.c > > > +++ b/read-cache.c > > > @@ -3126,6 +3126,7 @@ out: > > > free_hashfile(f); > > > strbuf_release(&sb); > > > free(ieot); > > > + free(eoie_c); > > > return ret; > > > } > > > > Yup, this one looks correct. I've sent out an equivalent patch via [1] a > > couple hours ago. > > > > Patrick > > > > [1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/ > > Sorry for the collision. I had checked when prepping the GGG PR on > Friday but forgot to check again before submitting. Your patch is > better in substance and context. Nothing to be sorry about, both series were sent out quite close to one another. Quite on the contrary, thanks for fixing this leak :) I don't mind much which of these versions lands in the tree, and the resulting conflict is trivial to solve anyway. Patrick ``` ## Derrick Stolee, 2024-10-01 13:20 Subject: Re: [PATCH 1/2] read-cache: free threaded memory pool Message-ID: <8ebebcd5-4ddb-4c1e-9bf8-4e9a79944e2b@gmail.com> URL: https://gitlist.dev/e/8ebebcd5-4ddb-4c1e-9bf8-4e9a79944e2b%40gmail.com In-Reply-To: ``` On 9/30/24 8:32 AM, Patrick Steinhardt wrote: > On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote: >> From: Derrick Stolee >> >> In load_cache_entries_threaded(), each thread is allocated its own > > s/allocated/allocating/ You're right that the wording is awkward but I'm not thrilled with the suggested alternative. Perhaps "each thread allocates its own" >> memory pool. This pool needs to be cleaned up while closing the threads >> down, or it will be leaked. > Okay. We move over the contents of the pool, but forgot to free the pool > itself. As far as I can see the pool is always allocated and only used > in two functions, both of which assume that it is allocated. So I wonder > why it is allocated in the first place instead of making it a direct > member of `struct load_cache_entries_thread_data`. I took a look at what it would take to replace the pointer with an inline struct but found complications with situations such as the find_mem_pool() method. While we could replace some of the logic to recognize the new type, the existing logic seems to depend on using the NULL pointer as an indicator that the pool should be lazily initialized. If we were to pull the struct inline, we would either need another boolean to indicate initialization or lose lazy initialization. I'm leaning towards the simpler leak fix over the disruption of that change. Thanks, -Stolee ``` ## Patrick Steinhardt, 2024-10-01 14:11 Subject: Re: [PATCH 1/2] read-cache: free threaded memory pool Message-ID: URL: https://gitlist.dev/e/ZvwDEyhe-3DyQp75%40pks.im In-Reply-To: <8ebebcd5-4ddb-4c1e-9bf8-4e9a79944e2b@gmail.com> ``` On Tue, Oct 01, 2024 at 09:20:01AM -0400, Derrick Stolee wrote: > On 9/30/24 8:32 AM, Patrick Steinhardt wrote: > > On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote: > > > From: Derrick Stolee > > > > > > In load_cache_entries_threaded(), each thread is allocated its own > > > > s/allocated/allocating/ > > You're right that the wording is awkward but I'm not thrilled with the > suggested alternative. > > Perhaps "each thread allocates its own" Sure, works for me :) > > > memory pool. This pool needs to be cleaned up while closing the threads > > > down, or it will be leaked. > > > Okay. We move over the contents of the pool, but forgot to free the pool > > itself. As far as I can see the pool is always allocated and only used > > in two functions, both of which assume that it is allocated. So I wonder > > why it is allocated in the first place instead of making it a direct > > member of `struct load_cache_entries_thread_data`. > > I took a look at what it would take to replace the pointer with an inline > struct but found complications with situations such as the find_mem_pool() > method. While we could replace some of the logic to recognize the new > type, the existing logic seems to depend on using the NULL pointer as an > indicator that the pool should be lazily initialized. > > If we were to pull the struct inline, we would either need another boolean > to indicate initialization or lose lazy initialization. > > I'm leaning towards the simpler leak fix over the disruption of that > change. Fair enough, no complaint from my side. I thought it would've been easy, but didn't dive deep. So if you say it is harder than I made it out to be with my shallow understanding I'm going to trust your judgement. After all, the leak fix is a strict improvement by itself. Patrick ``` ## Derrick Stolee via GitGitGadget, 2024-10-01 17:37 Subject: [PATCH v2] read-cache: free threaded memory pool Message-ID: URL: https://gitlist.dev/e/pull.1801.v2.git.1727804265033.gitgitgadget%40gmail.com In-Reply-To: ``` From: Derrick Stolee In load_cache_entries_threaded(), each thread allocates its own memory pool. This pool needs to be cleaned up while closing the threads down, or it will be leaked. This ce_mem_pool pointer could theoretically be converted to an inline copy of the struct, but the use of a pointer helps with existing lazy- initialization logic. Adjusting that behavior only to avoid this pointer would be a much bigger change. Signed-off-by: Derrick Stolee --- read-cache: two small leak fixes This v2 removes the duplicate patch and updates the commit message. Thanks, -Stolee Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1801%2Fderrickstolee%2Fleaks-v2 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1801/derrickstolee/leaks-v2 Pull-Request: https://github.com/gitgitgadget/git/pull/1801 Range-diff vs v1: 1: 9a45b15ea4b ! 1: 220a098c93c read-cache: free threaded memory pool @@ Metadata ## Commit message ## read-cache: free threaded memory pool - In load_cache_entries_threaded(), each thread is allocated its own - memory pool. This pool needs to be cleaned up while closing the threads - down, or it will be leaked. + In load_cache_entries_threaded(), each thread allocates its own memory + pool. This pool needs to be cleaned up while closing the threads down, + or it will be leaked. + + This ce_mem_pool pointer could theoretically be converted to an inline + copy of the struct, but the use of a pointer helps with existing lazy- + initialization logic. Adjusting that behavior only to avoid this pointer + would be a much bigger change. Signed-off-by: Derrick Stolee 2: b6fe5b3ef7e < -: ----------- read-cache: free hash context in do_write_index() read-cache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/read-cache.c b/read-cache.c index 764fdfec465..3c078afadbc 100644 --- a/read-cache.c +++ b/read-cache.c @@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con if (err) die(_("unable to join load_cache_entries thread: %s"), strerror(err)); mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool); + free(p->ce_mem_pool); consumed += p->consumed; } base-commit: 6258f68c3c1092c901337895c864073dcdea9213 -- gitgitgadget ``` ## Patrick Steinhardt, 2024-10-02 10:49 Subject: Re: [PATCH v2] read-cache: free threaded memory pool Message-ID: URL: https://gitlist.dev/e/Zv0lISjo-5bHzEzW%40pks.im In-Reply-To: ``` On Tue, Oct 01, 2024 at 05:37:44PM +0000, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee > > In load_cache_entries_threaded(), each thread allocates its own memory > pool. This pool needs to be cleaned up while closing the threads down, > or it will be leaked. > > This ce_mem_pool pointer could theoretically be converted to an inline > copy of the struct, but the use of a pointer helps with existing lazy- > initialization logic. Adjusting that behavior only to avoid this pointer > would be a much bigger change. Thanks, this looks good to me. Patrick ```