From: David Howells <dhowells@redhat.com> To: Peter Zijlstra <peterz@infradead.org> Cc: dhowells@redhat.com, Jann Horn <jannh@google.com>, Greg KH <gregkh@linuxfoundation.org>, Al Viro <viro@zeniv.linux.org.uk>, raven@themaw.net, linux-fsdevel <linux-fsdevel@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>, linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module <linux-security-module@vger.kernel.org>, kernel list <linux-kernel@vger.kernel.org>, Kees Cook <keescook@chromium.org>, Kernel Hardening <kernel-hardening@lists.openwall.com> Subject: Re: [PATCH 1/7] General notification queue with user mmap()'able ring buffer Date: Fri, 31 May 2019 15:20:12 +0100 [thread overview] Message-ID: <606.1559312412@warthog.procyon.org.uk> (raw) In-Reply-To: <20190531132620.GC2606@hirez.programming.kicks-ass.net> Peter Zijlstra <peterz@infradead.org> wrote: > Is it not the responsibility of the task that affects the 1->0 > transition to actually free the memory? > > That is, I'm expecting the '...' in both cases above the include the > actual freeing of the object. If this is not the case, then @usage is > not a reference count. Yes. The '...' does the freeing. It seemed unnecessary to include the code ellipsised there since it's not the point of the discussion, but if you want the full function: void afs_put_call(struct afs_call *call) { struct afs_net *net = call->net; int n = atomic_dec_return(&call->usage); int o = atomic_read(&net->nr_outstanding_calls); trace_afs_call(call, afs_call_trace_put, n + 1, o, __builtin_return_address(0)); ASSERTCMP(n, >=, 0); if (n == 0) { ASSERT(!work_pending(&call->async_work)); ASSERT(call->type->name != NULL); if (call->rxcall) { rxrpc_kernel_end_call(net->socket, call->rxcall); call->rxcall = NULL; } if (call->type->destructor) call->type->destructor(call); afs_put_server(call->net, call->server); afs_put_cb_interest(call->net, call->cbi); afs_put_addrlist(call->alist); kfree(call->request); trace_afs_call(call, afs_call_trace_free, 0, o, __builtin_return_address(0)); kfree(call); o = atomic_dec_return(&net->nr_outstanding_calls); if (o == 0) wake_up_var(&net->nr_outstanding_calls); } } You can see the kfree(call) in there. Peter Zijlstra <peterz@infradead.org> wrote: > (and it has already been established that refcount_t doesn't work for > usage count scenarios) ? Does that mean struct kref doesn't either? > Aside from that, is the problem that refcount_dec_and_test() returns a > boolean (true - last put, false - not last) instead of the refcount > value? This does indeed make it hard to print the exact count value for > the event. That is the problem, yes - well, one of them: refcount_inc() doesn't either. David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com> To: Peter Zijlstra <peterz@infradead.org> Cc: dhowells@redhat.com, Jann Horn <jannh@google.com>, Greg KH <gregkh@linuxfoundation.org>, Al Viro <viro@zeniv.linux.org.uk>, raven@themaw.net, linux-fsdevel <linux-fsdevel@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>, linux-block@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module <linux-security-module@vger.kernel.org>, kernel list <linux-kernel@vger.kernel.org>, Kees Cook <keescook@chromium.org>, Kernel Hardening <kernel-hardening@lists.openwall.com> Subject: Re: [PATCH 1/7] General notification queue with user mmap()'able ring buffer Date: Fri, 31 May 2019 14:20:12 +0000 [thread overview] Message-ID: <606.1559312412@warthog.procyon.org.uk> (raw) In-Reply-To: <20190531132620.GC2606@hirez.programming.kicks-ass.net> Peter Zijlstra <peterz@infradead.org> wrote: > Is it not the responsibility of the task that affects the 1->0 > transition to actually free the memory? > > That is, I'm expecting the '...' in both cases above the include the > actual freeing of the object. If this is not the case, then @usage is > not a reference count. Yes. The '...' does the freeing. It seemed unnecessary to include the code ellipsised there since it's not the point of the discussion, but if you want the full function: void afs_put_call(struct afs_call *call) { struct afs_net *net = call->net; int n = atomic_dec_return(&call->usage); int o = atomic_read(&net->nr_outstanding_calls); trace_afs_call(call, afs_call_trace_put, n + 1, o, __builtin_return_address(0)); ASSERTCMP(n, >=, 0); if (n = 0) { ASSERT(!work_pending(&call->async_work)); ASSERT(call->type->name != NULL); if (call->rxcall) { rxrpc_kernel_end_call(net->socket, call->rxcall); call->rxcall = NULL; } if (call->type->destructor) call->type->destructor(call); afs_put_server(call->net, call->server); afs_put_cb_interest(call->net, call->cbi); afs_put_addrlist(call->alist); kfree(call->request); trace_afs_call(call, afs_call_trace_free, 0, o, __builtin_return_address(0)); kfree(call); o = atomic_dec_return(&net->nr_outstanding_calls); if (o = 0) wake_up_var(&net->nr_outstanding_calls); } } You can see the kfree(call) in there. Peter Zijlstra <peterz@infradead.org> wrote: > (and it has already been established that refcount_t doesn't work for > usage count scenarios) ? Does that mean struct kref doesn't either? > Aside from that, is the problem that refcount_dec_and_test() returns a > boolean (true - last put, false - not last) instead of the refcount > value? This does indeed make it hard to print the exact count value for > the event. That is the problem, yes - well, one of them: refcount_inc() doesn't either. David
next prev parent reply other threads:[~2019-05-31 14:20 UTC|newest] Thread overview: 131+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-05-28 16:01 [RFC][PATCH 0/7] Mount, FS, Block and Keyrings notifications David Howells 2019-05-28 16:01 ` David Howells 2019-05-28 16:01 ` [PATCH 1/7] General notification queue with user mmap()'able ring buffer David Howells 2019-05-28 16:01 ` David Howells 2019-05-28 16:26 ` Greg KH 2019-05-28 16:26 ` Greg KH 2019-05-28 17:30 ` David Howells 2019-05-28 17:30 ` David Howells 2019-05-28 23:12 ` Greg KH 2019-05-28 23:12 ` Greg KH 2019-05-29 16:06 ` David Howells 2019-05-29 16:06 ` David Howells 2019-05-29 17:46 ` Jann Horn 2019-05-29 17:46 ` Jann Horn 2019-05-29 21:02 ` David Howells 2019-05-29 21:02 ` David Howells 2019-05-31 11:14 ` Peter Zijlstra 2019-05-31 11:14 ` Peter Zijlstra 2019-05-31 12:02 ` David Howells 2019-05-31 12:02 ` David Howells 2019-05-31 13:26 ` Peter Zijlstra 2019-05-31 13:26 ` Peter Zijlstra 2019-05-31 14:20 ` David Howells [this message] 2019-05-31 14:20 ` David Howells 2019-05-31 16:44 ` Peter Zijlstra 2019-05-31 16:44 ` Peter Zijlstra 2019-05-31 17:12 ` David Howells 2019-05-31 17:12 ` David Howells 2019-06-17 16:24 ` Peter Zijlstra 2019-06-17 16:24 ` Peter Zijlstra 2019-05-29 23:09 ` Greg KH 2019-05-29 23:09 ` Greg KH 2019-05-29 23:11 ` Greg KH 2019-05-29 23:11 ` Greg KH 2019-05-30 9:50 ` Andrea Parri 2019-05-30 9:50 ` Andrea Parri 2019-05-31 8:35 ` Peter Zijlstra 2019-05-31 8:35 ` Peter Zijlstra 2019-05-31 8:47 ` Peter Zijlstra 2019-05-31 8:47 ` Peter Zijlstra 2019-05-31 12:42 ` David Howells 2019-05-31 12:42 ` David Howells 2019-05-31 14:55 ` David Howells 2019-05-31 14:55 ` David Howells 2019-05-28 19:14 ` Jann Horn 2019-05-28 19:14 ` Jann Horn 2019-05-28 22:28 ` David Howells 2019-05-28 22:28 ` David Howells 2019-05-28 23:16 ` Jann Horn 2019-05-28 23:16 ` Jann Horn 2019-05-28 16:02 ` [PATCH 2/7] keys: Add a notification facility David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 16:02 ` [PATCH 3/7] vfs: Add a mount-notification facility David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 20:06 ` Jann Horn 2019-05-28 20:06 ` Jann Horn 2019-05-28 23:04 ` David Howells 2019-05-28 23:04 ` David Howells 2019-05-28 23:23 ` Jann Horn 2019-05-28 23:23 ` Jann Horn 2019-05-29 11:16 ` David Howells 2019-05-29 11:16 ` David Howells 2019-05-28 23:08 ` David Howells 2019-05-28 23:08 ` David Howells 2019-05-29 10:55 ` David Howells 2019-05-29 10:55 ` David Howells 2019-05-29 11:00 ` David Howells 2019-05-29 11:00 ` David Howells 2019-05-29 15:53 ` Casey Schaufler 2019-05-29 15:53 ` Casey Schaufler 2019-05-29 16:12 ` Jann Horn 2019-05-29 16:12 ` Jann Horn 2019-05-29 17:04 ` Casey Schaufler 2019-05-29 17:04 ` Casey Schaufler 2019-06-03 16:30 ` David Howells 2019-06-03 16:30 ` David Howells 2019-05-29 17:13 ` Andy Lutomirski 2019-05-29 17:13 ` Andy Lutomirski 2019-05-29 17:46 ` Casey Schaufler 2019-05-29 17:46 ` Casey Schaufler 2019-05-29 18:11 ` Jann Horn 2019-05-29 18:11 ` Jann Horn 2019-05-29 19:28 ` Casey Schaufler 2019-05-29 19:28 ` Casey Schaufler 2019-05-29 19:47 ` Jann Horn 2019-05-29 19:47 ` Jann Horn 2019-05-29 20:50 ` Casey Schaufler 2019-05-29 20:50 ` Casey Schaufler 2019-05-29 23:12 ` Andy Lutomirski 2019-05-29 23:12 ` Andy Lutomirski 2019-05-29 23:56 ` Casey Schaufler 2019-05-29 23:56 ` Casey Schaufler 2019-05-28 16:02 ` [PATCH 4/7] vfs: Add superblock notifications David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 20:27 ` Jann Horn 2019-05-28 20:27 ` Jann Horn 2019-05-29 12:58 ` David Howells 2019-05-29 12:58 ` David Howells 2019-05-29 14:16 ` Jann Horn 2019-05-29 14:16 ` Jann Horn 2019-05-28 16:02 ` [PATCH 5/7] fsinfo: Export superblock notification counter David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 16:02 ` [PATCH 6/7] block: Add block layer notifications David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 20:37 ` Jann Horn 2019-05-28 20:37 ` Jann Horn 2019-05-28 16:02 ` [PATCH 7/7] Add sample notification program David Howells 2019-05-28 16:02 ` David Howells 2019-05-28 23:58 ` [RFC][PATCH 0/7] Mount, FS, Block and Keyrings notifications Greg KH 2019-05-28 23:58 ` Greg KH 2019-05-29 6:33 ` Amir Goldstein 2019-05-29 6:33 ` Amir Goldstein 2019-05-29 6:33 ` Amir Goldstein 2019-05-29 14:25 ` Jan Kara 2019-05-29 14:25 ` Jan Kara 2019-05-29 15:10 ` Greg KH 2019-05-29 15:10 ` Greg KH 2019-05-29 15:53 ` Amir Goldstein 2019-05-29 15:53 ` Amir Goldstein 2019-05-30 11:00 ` Jan Kara 2019-05-30 11:00 ` Jan Kara 2019-06-04 12:33 ` David Howells 2019-06-04 12:33 ` David Howells 2019-05-29 6:45 ` David Howells 2019-05-29 6:45 ` David Howells 2019-05-29 7:40 ` Amir Goldstein 2019-05-29 7:40 ` Amir Goldstein 2019-05-29 9:09 ` David Howells 2019-05-29 9:09 ` David Howells 2019-05-29 15:41 ` Casey Schaufler 2019-05-29 15:41 ` Casey Schaufler
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