Re: [PATCH] make setpriority POSIX compliant; introduce PRIO_THREADextension

From: Chris Friesen
Date: Tue Sep 09 2008 - 12:43:31 EST

Michael Kerrisk wrote:

On 9/1/08, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
Since there may be programs which use the fact that

setpriority(PRIO_PROCESS, tid, value)

prior to this patch was setting priority for selected thread,
this behavior is retained in case when tid != pid.

IOW: with PRIO_PROCESS, if pid specifies a thread group leader,
all threads' prios are set. Otherwise, only selected thread's priority
is set. (Alternative can be to just fail with ESRCH).

I would expect
setpriority(PRIO_PROCESS, getpid())
setpriority(PRIO_PROCESS, 0)
to have the same affect (because: which == PRIO_PRCESS, who == 0
conventionally means "the calling process").

But they do not: the latter call only changes the priority of the
calling thread. Is this intended?

The patch interprets 0 as the current pid rather than the current tgid.

It's up for discussion whether we should preserve old behaviour when specifying 0, or use a new and arguably more logical behaviour but possibly break old apps.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at