Since commit 43e23b6c0b01 ("debugfs: log errors when something goes wrong")
debugfs logs attempts to create existing files.
However binder attempts to create multiple debugfs files with
the same name when a single PID has multiple contexts, this leads
to log spamming during an Android boot (17 such messages during
boot on my system).
Fix this by checking if we already know the PID and only create
the debugfs entry for the first context per PID.
Do the same thing for binderfs for symmetry.
Signed-off-by: Martin Fuzzey <[email protected]>
---
drivers/android/binder.c | 37 +++++++++++++++++++------------------
1 file changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 976a694..254f87b 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5203,10 +5203,11 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
static int binder_open(struct inode *nodp, struct file *filp)
{
- struct binder_proc *proc;
+ struct binder_proc *proc, *itr;
struct binder_device *binder_dev;
struct binderfs_info *info;
struct dentry *binder_binderfs_dir_entry_proc = NULL;
+ bool existing_pid = false;
binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d:%d\n", __func__,
current->group_leader->pid, current->pid);
@@ -5239,19 +5240,24 @@ static int binder_open(struct inode *nodp, struct file *filp)
filp->private_data = proc;
mutex_lock(&binder_procs_lock);
+ hlist_for_each_entry(itr, &binder_procs, proc_node) {
+ if (itr->pid == proc->pid) {
+ existing_pid = true;
+ break;
+ }
+ }
hlist_add_head(&proc->proc_node, &binder_procs);
mutex_unlock(&binder_procs_lock);
- if (binder_debugfs_dir_entry_proc) {
+ if (binder_debugfs_dir_entry_proc && !existing_pid) {
char strbuf[11];
snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);
/*
- * proc debug entries are shared between contexts, so
- * this will fail if the process tries to open the driver
- * again with a different context. The priting code will
- * anyway print all contexts that a given PID has, so this
- * is not a problem.
+ * proc debug entries are shared between contexts.
+ * Only create for the first PID to avoid debugfs log spamming
+ * The printing code will anyway print all contexts for a given
+ * PID so this is not a problem.
*/
proc->debugfs_entry = debugfs_create_file(strbuf, 0444,
binder_debugfs_dir_entry_proc,
@@ -5259,19 +5265,16 @@ static int binder_open(struct inode *nodp, struct file *filp)
&proc_fops);
}
- if (binder_binderfs_dir_entry_proc) {
+ if (binder_binderfs_dir_entry_proc && !existing_pid) {
char strbuf[11];
struct dentry *binderfs_entry;
snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);
/*
* Similar to debugfs, the process specific log file is shared
- * between contexts. If the file has already been created for a
- * process, the following binderfs_create_file() call will
- * fail with error code EEXIST if another context of the same
- * process invoked binder_open(). This is ok since same as
- * debugfs, the log file will contain information on all
- * contexts of a given PID.
+ * between contexts. Only create for the first PID.
+ * This is ok since same as debugfs, the log file will contain
+ * information on all contexts of a given PID.
*/
binderfs_entry = binderfs_create_file(binder_binderfs_dir_entry_proc,
strbuf, &proc_fops, (void *)(unsigned long)proc->pid);
@@ -5281,10 +5284,8 @@ static int binder_open(struct inode *nodp, struct file *filp)
int error;
error = PTR_ERR(binderfs_entry);
- if (error != -EEXIST) {
- pr_warn("Unable to create file %s in binderfs (error %d)\n",
- strbuf, error);
- }
+ pr_warn("Unable to create file %s in binderfs (error %d)\n",
+ strbuf, error);
}
}
--
1.9.1
On Fri, Jan 10, 2020 at 04:44:01PM +0100, Martin Fuzzey wrote:
> Since commit 43e23b6c0b01 ("debugfs: log errors when something goes wrong")
> debugfs logs attempts to create existing files.
>
> However binder attempts to create multiple debugfs files with
> the same name when a single PID has multiple contexts, this leads
> to log spamming during an Android boot (17 such messages during
> boot on my system).
>
> Fix this by checking if we already know the PID and only create
> the debugfs entry for the first context per PID.
>
> Do the same thing for binderfs for symmetry.
>
> Signed-off-by: Martin Fuzzey <[email protected]>
Does this need a "Fixes:" and cc: stable tag?
And it would be good to get a review from the binder maintainer(s) to
see if this is sane or not...
thanks,
greg k-h
On Tue, Jan 14, 2020 at 7:22 AM Greg Kroah-Hartman
<[email protected]> wrote:
>
> On Fri, Jan 10, 2020 at 04:44:01PM +0100, Martin Fuzzey wrote:
> > Since commit 43e23b6c0b01 ("debugfs: log errors when something goes wrong")
> > debugfs logs attempts to create existing files.
> >
> > However binder attempts to create multiple debugfs files with
> > the same name when a single PID has multiple contexts, this leads
> > to log spamming during an Android boot (17 such messages during
> > boot on my system).
> >
> > Fix this by checking if we already know the PID and only create
> > the debugfs entry for the first context per PID.
> >
> > Do the same thing for binderfs for symmetry.
> >
> > Signed-off-by: Martin Fuzzey <[email protected]>
>
> Does this need a "Fixes:" and cc: stable tag?
It would probably make sense to take it into 5.4 (spam issue was
introduced in 5.2).
Please add "Fixes:" as Greg suggests citing the commit above.
Acked-by: Todd Kjos <[email protected]>
>
> And it would be good to get a review from the binder maintainer(s) to
> see if this is sane or not...
>
> thanks,
>
> greg k-h