diff options
| author | Jiri Kosina <jkosina@suse.cz> | 2022-01-10 09:56:57 +0100 |
|---|---|---|
| committer | Jiri Kosina <jkosina@suse.cz> | 2022-01-10 09:56:57 +0100 |
| commit | 3551a3ff8229e15d2a4b47b8234923bc72da65ef (patch) | |
| tree | a62465753397b0268529a5d0b9ab43a8840069ad /Documentation/locking/locktypes.rst | |
| parent | 906095af85e8b2e53ee9f8c50b3dff365aa09df8 (diff) | |
| parent | 33a5c2793451770cb6dcf0cc35c76cfd4b045513 (diff) | |
| download | linux-3551a3ff8229e15d2a4b47b8234923bc72da65ef.tar.gz linux-3551a3ff8229e15d2a4b47b8234923bc72da65ef.tar.bz2 linux-3551a3ff8229e15d2a4b47b8234923bc72da65ef.zip | |
Merge branch 'for-5.17/letsketch' into for-linus
- new driver to support for LetSketch device (Hans de Goede)
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() { |