diff options
| author | Anton Blanchard <anton@samba.org> | 2012-01-09 14:29:15 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-01-11 11:54:20 +1100 |
| commit | a5ccfee05a439b803640e94584056204501db31c (patch) | |
| tree | 2545bab092fe62924d5ccba8920c137b1e771ba6 /arch/powerpc/platforms/pseries/lpar.c | |
| parent | 7b3480f8b701170c046e1ed362946f5f0d005e13 (diff) | |
| download | linux-a5ccfee05a439b803640e94584056204501db31c.tar.gz | |
powerpc: Fix RCU idle and hcall tracing
Tracepoints should not be called inside an rcu_idle_enter/rcu_idle_exit
region. Since pSeries calls H_CEDE in the idle loop, we were violating
this rule.
commit a7b152d5342c (powerpc: Tell RCU about idle after hcall tracing)
tried to work around it by delaying the rcu_idle_enter until after we
called the hcall tracepoint, but there are a number of issues with it.
The hcall tracepoint trampoline code is called conditionally when the
tracepoint is enabled. If the tracepoint is not enabled we never call
rcu_idle_enter. The idle_uses_rcu check was also done at compile time
which breaks multiplatform builds.
The simple fix is to avoid tracing H_CEDE and rely on other tracepoints
and the hypervisor dispatch trace log to work out if we called H_CEDE.
This fixes a hang during boot on pSeries.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/platforms/pseries/lpar.c')
| -rw-r--r-- | arch/powerpc/platforms/pseries/lpar.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 948e0e3b3547a..7bc73af6c7b9e 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -546,6 +546,13 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) unsigned long flags; unsigned int *depth; + /* + * We cannot call tracepoints inside RCU idle regions which + * means we must not trace H_CEDE. + */ + if (opcode == H_CEDE) + return; + local_irq_save(flags); depth = &__get_cpu_var(hcall_trace_depth); @@ -556,8 +563,6 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) (*depth)++; preempt_disable(); trace_hcall_entry(opcode, args); - if (opcode == H_CEDE) - rcu_idle_enter(); (*depth)--; out: @@ -570,6 +575,9 @@ void __trace_hcall_exit(long opcode, unsigned long retval, unsigned long flags; unsigned int *depth; + if (opcode == H_CEDE) + return; + local_irq_save(flags); depth = &__get_cpu_var(hcall_trace_depth); @@ -578,8 +586,6 @@ void __trace_hcall_exit(long opcode, unsigned long retval, goto out; (*depth)++; - if (opcode == H_CEDE) - rcu_idle_exit(); trace_hcall_exit(opcode, retval, retbuf); preempt_enable(); (*depth)--; |