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| author | Jakub Kicinski <kuba@kernel.org> | 2021-12-09 12:04:19 -0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-12-09 13:23:02 -0800 |
| commit | 3150a73366b64e3109f0facbc98bcacbc14e81ba (patch) | |
| tree | 2b94b32c5fe97a4e76058a6f65e8c5717b53ee16 /Documentation/locking/locktypes.rst | |
| parent | 1a2fb220edca98d18f90e3ef5bd6853a6b22b1b8 (diff) | |
| parent | ded746bfc94398d2ee9de315a187677b207b2004 (diff) | |
| download | linux-3150a73366b64e3109f0facbc98bcacbc14e81ba.tar.gz linux-3150a73366b64e3109f0facbc98bcacbc14e81ba.tar.bz2 linux-3150a73366b64e3109f0facbc98bcacbc14e81ba.zip | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
No conflicts.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/locking/locktypes.rst')
| -rw-r--r-- | Documentation/locking/locktypes.rst | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/Documentation/locking/locktypes.rst b/Documentation/locking/locktypes.rst index ddada4a53749..4fd7b70fcde1 100644 --- a/Documentation/locking/locktypes.rst +++ b/Documentation/locking/locktypes.rst @@ -439,11 +439,9 @@ preemption. The following substitution works on both kernels:: spin_lock(&p->lock); p->count += this_cpu_read(var2); -On a non-PREEMPT_RT kernel migrate_disable() maps to preempt_disable() -which makes the above code fully equivalent. On a PREEMPT_RT kernel migrate_disable() ensures that the task is pinned on the current CPU which in turn guarantees that the per-CPU access to var1 and var2 are staying on -the same CPU. +the same CPU while the task remains preemptible. The migrate_disable() substitution is not valid for the following scenario:: @@ -456,9 +454,8 @@ scenario:: p = this_cpu_ptr(&var1); p->val = func2(); -While correct on a non-PREEMPT_RT kernel, this breaks on PREEMPT_RT because -here migrate_disable() does not protect against reentrancy from a -preempting task. A correct substitution for this case is:: +This breaks because migrate_disable() does not protect against reentrancy from +a preempting task. A correct substitution for this case is:: func() { |