diff mbox series

[bpf-next,6/9] bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check

Message ID 20221025184524.3526117-7-martin.lau@linux.dev (mailing list archive)
State Accepted
Commit fda64ae0bb3e37b5a4292625c6931cb156224d0f
Delegated to: BPF
Headers show
Series bpf: Avoid unnecessary deadlock detection and failure in task storage | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers warning 7 maintainers not CCed: sdf@google.com john.fastabend@gmail.com yhs@fb.com haoluo@google.com jolsa@kernel.org kpsingh@kernel.org song@kernel.org
netdev/build_clang success Errors and warnings before: 5 this patch: 5
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 52 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
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Commit Message

Martin KaFai Lau Oct. 25, 2022, 6:45 p.m. UTC 
From: Martin KaFai Lau <martin.lau@kernel.org>

Similar to the earlier change in bpf_task_storage_get_recur.
This patch changes bpf_task_storage_delete_recur such that it
does the lookup first.  It only returns -EBUSY if it needs to
take the spinlock to do the deletion when potential deadlock
is detected.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
 kernel/bpf/bpf_task_storage.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index c3a841be438f..f3f79b618a68 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -184,7 +184,8 @@  static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 	return err;
 }
 
-static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
+static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
+			       bool nobusy)
 {
 	struct bpf_local_storage_data *sdata;
 
@@ -192,6 +193,9 @@  static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
 	if (!sdata)
 		return -ENOENT;
 
+	if (!nobusy)
+		return -EBUSY;
+
 	bpf_selem_unlink(SELEM(sdata), true);
 
 	return 0;
@@ -220,7 +224,7 @@  static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
 	}
 
 	bpf_task_storage_lock();
-	err = task_storage_delete(task, map);
+	err = task_storage_delete(task, map, true);
 	bpf_task_storage_unlock();
 out:
 	put_pid(pid);
@@ -289,21 +293,21 @@  BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
 BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *,
 	   task)
 {
+	bool nobusy;
 	int ret;
 
 	WARN_ON_ONCE(!bpf_rcu_lock_held());
 	if (!task)
 		return -EINVAL;
 
-	if (!bpf_task_storage_trylock())
-		return -EBUSY;
-
+	nobusy = bpf_task_storage_trylock();
 	/* This helper must only be called from places where the lifetime of the task
 	 * is guaranteed. Either by being refcounted or by being protected
 	 * by an RCU read-side critical section.
 	 */
-	ret = task_storage_delete(task, map);
-	bpf_task_storage_unlock();
+	ret = task_storage_delete(task, map, nobusy);
+	if (nobusy)
+		bpf_task_storage_unlock();
 	return ret;
 }