diff options
| author |   Thomas Gleixner <tglx@linutronix.de> | 2020-06-11 15:17:57 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-06-11 15:17:57 +0200 |
| commit | f77d26a9fc525286bcef3d4f98b52e17482cf49c (patch) | |
| tree | 6b179c9aa84787773cb601a14a64255e2912154b /include/linux/swait.h | |
| parent | EDAC/amd64: Add AMD family 17h model 60h PCI IDs (diff) | |
| parent | x86/entry: Unbreak __irqentry_text_start/end magic (diff) | |
| download | wireguard-linux-f77d26a9fc525286bcef3d4f98b52e17482cf49c.tar.xz wireguard-linux-f77d26a9fc525286bcef3d4f98b52e17482cf49c.zip | |
Merge branch 'x86/entry' into ras/core
to fixup conflicts in arch/x86/kernel/cpu/mce/core.c so MCE specific follow
up patches can be applied without creating a horrible merge conflict
afterwards.
Diffstat (limited to 'include/linux/swait.h')
| -rw-r--r-- | include/linux/swait.h | 23 |
1 files changed, 5 insertions, 18 deletions
diff --git a/include/linux/swait.h b/include/linux/swait.h index 73e06e9986d4..6a8c22b8c2a5 100644 --- a/include/linux/swait.h +++ b/include/linux/swait.h @@ -9,23 +9,10 @@ #include <asm/current.h> /* - * BROKEN wait-queues. - * - * These "simple" wait-queues are broken garbage, and should never be - * used. The comments below claim that they are "similar" to regular - * wait-queues, but the semantics are actually completely different, and - * every single user we have ever had has been buggy (or pointless). - * - * A "swake_up_one()" only wakes up _one_ waiter, which is not at all what - * "wake_up()" does, and has led to problems. In other cases, it has - * been fine, because there's only ever one waiter (kvm), but in that - * case gthe whole "simple" wait-queue is just pointless to begin with, - * since there is no "queue". Use "wake_up_process()" with a direct - * pointer instead. - * - * While these are very similar to regular wait queues (wait.h) the most - * important difference is that the simple waitqueue allows for deterministic - * behaviour -- IOW it has strictly bounded IRQ and lock hold times. + * Simple waitqueues are semantically very different to regular wait queues + * (wait.h). The most important difference is that the simple waitqueue allows + * for deterministic behaviour -- IOW it has strictly bounded IRQ and lock hold + * times. * * Mainly, this is accomplished by two things. Firstly not allowing swake_up_all * from IRQ disabled, and dropping the lock upon every wakeup, giving a higher @@ -39,7 +26,7 @@ * sleeper state. * * - the !exclusive mode; because that leads to O(n) wakeups, everything is - * exclusive. + * exclusive. As such swake_up_one will only ever awake _one_ waiter. * * - custom wake callback functions; because you cannot give any guarantees * about random code. This also allows swait to be used in RT, such that |