On 17/06/2016 18:33, Alex Bennée wrote: > Each time watchpoints are added/removed from the array it's done using > an read-copy-update cycle. Simultaneous writes are protected by the > debug_update_lock. > > Signed-off-by: Alex Bennée <alex.ben...@linaro.org> > --- > cpu-exec.c | 7 ++- > exec.c | 193 > ++++++++++++++++++++++++++++++++++++++++++++----------------- > 2 files changed, 144 insertions(+), 56 deletions(-) > > diff --git a/cpu-exec.c b/cpu-exec.c > index 2736a27..7fcb500 100644 > --- a/cpu-exec.c > +++ b/cpu-exec.c > @@ -387,12 +387,13 @@ static inline bool cpu_handle_halt(CPUState *cpu) > static inline void cpu_handle_debug_exception(CPUState *cpu) > { > CPUClass *cc = CPU_GET_CLASS(cpu); > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); > CPUWatchpoint *wp; > int i; > > - if (!cpu->watchpoint_hit && cpu->watchpoints) { > - for (i = 0; i < cpu->watchpoints->len; i++) { > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); > + if (!cpu->watchpoint_hit && wpts) { > + for (i = 0; i < wpts->len; i++) { > + wp = &g_array_index(wpts, CPUWatchpoint, i); > wp->flags &= ~BP_WATCHPOINT_HIT; > } > } > diff --git a/exec.c b/exec.c > index d1d14c1..b9167ec 100644 > --- a/exec.c > +++ b/exec.c > @@ -735,6 +735,18 @@ static void breakpoint_invalidate(CPUState *cpu, > target_ulong pc) > } > #endif > > +struct FreeDebugRCU { > + struct rcu_head rcu; > + GArray *debug; > +};
Deja vu? ;) > +/* RCU reclaim step */ > +static void rcu_debug_free(struct FreeDebugRCU *rcu_free) > +{ > + g_array_free(rcu_free->debug, false); > + g_free(rcu_free); > +} > + > #if defined(CONFIG_USER_ONLY) > void cpu_watchpoint_remove_all(CPUState *cpu, int mask) > > @@ -766,22 +778,72 @@ CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, > int ref) > return NULL; > } > #else > -/* Find watchpoint with external reference */ > -CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, int ref) > +/* Create a working copy of the watchpoints. > + * > + * The rcu_read_lock() may already be held depending on where this > + * update has been triggered from. However it is safe to nest > + * rcu_read_locks() so we do the copy under the lock here. Same as patch 5. > + */ > + > +static GArray *rcu_copy_watchpoints(CPUState *cpu) > { > - CPUWatchpoint *wp = NULL; > + GArray *old, *new; > + > + rcu_read_lock(); > + old = atomic_rcu_read(&cpu->watchpoints); > + if (old) { > + new = g_array_sized_new(false, false, sizeof(CPUWatchpoint), > old->len); > + memcpy(new->data, old->data, old->len * sizeof(CPUWatchpoint)); > + new->len = old->len; > + } else { > + new = g_array_new(false, false, sizeof(CPUWatchpoint)); > + } > + rcu_read_unlock(); > + > + return new; > +} > + > +/* Called with update lock held */ > +static void rcu_update_watchpoints(CPUState *cpu, GArray *new_watchpts) > +{ > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); > + atomic_rcu_set(&cpu->watchpoints, new_watchpts); > + if (wpts) { > + struct FreeDebugRCU *rcu_free = g_malloc(sizeof(*rcu_free)); > + rcu_free->debug = wpts; > + call_rcu(rcu_free, rcu_debug_free, rcu); > + } > +} > + > +/* Find watchpoint with external reference, only valid for duration of > + * rcu_read_lock */ > +static CPUWatchpoint *find_watch_with_ref(GArray *wpts, int ref) watchpoint_get_by_ref. BTW, should the "ref" be unsigned? > +{ > + CPUWatchpoint *wp; > int i = 0; > + > do { > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i++); > - } while (i < cpu->watchpoints->len && wp && wp->ref != ref); > + wp = &g_array_index(wpts, CPUWatchpoint, i); > + if (wp->ref == ref) { > + return wp; > + } > + } while (i++ < wpts->len); > + > + return NULL; > +} > > - return wp; > +/* Find watchpoint with external reference */ > +CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, int ref) > +{ > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); > + return find_watch_with_ref(wpts, ref); > } > > /* Add a watchpoint. */ > int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr addr, vaddr len, > int flags, int ref) > { > + GArray *wpts; > CPUWatchpoint *wp = NULL; > > /* forbid ranges which are empty or run off the end of the address space > */ > @@ -791,14 +853,14 @@ int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr > addr, vaddr len, > return -EINVAL; > } > > - /* Allocate if no previous watchpoints */ > - if (!cpu->watchpoints) { > - cpu->watchpoints = g_array_new(false, true, sizeof(CPUWatchpoint)); > - } > + qemu_mutex_lock(&cpu->update_debug_lock); > + > + /* This will allocate if no previous breakpoints */ ^^^^^^^^^^^ watchpoints > + wpts = rcu_copy_watchpoints(cpu); In Linux it's usual to just call the array "new" (and if you need it "old"). I like it more than bpts and wpts. > > /* Find old watchpoint */ > if (ref != BPWP_NOREF) { > - wp = cpu_watchpoint_get_by_ref(cpu, ref); > + wp = find_watch_with_ref(wpts, ref); > } > > if (wp) { > @@ -815,15 +877,18 @@ int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr > addr, vaddr len, > > /* keep all GDB-injected watchpoints in front */ > if (flags & BP_GDB) { > - g_array_prepend_val(cpu->watchpoints, watch); > + g_array_prepend_val(wpts, watch); > } else { > - g_array_append_val(cpu->watchpoints, watch); > + g_array_append_val(wpts, watch); > } > } > > > tlb_flush_page(cpu, addr); > > + rcu_update_watchpoints(cpu, wpts); > + qemu_mutex_unlock(&cpu->update_debug_lock); > + > return 0; > } > > @@ -832,69 +897,101 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, > vaddr len, int flags) > return cpu_watchpoint_insert_with_ref(cpu, addr, len, flags, BPWP_NOREF); > } > > -static void cpu_watchpoint_delete(CPUState *cpu, int index) > +static void cpu_watchpoint_delete(CPUState *cpu, GArray *wpts, int index) Same here, just call the GArray "new". > { > CPUWatchpoint *wp; > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, index); > + wp = &g_array_index(wpts, CPUWatchpoint, index); > tlb_flush_page(cpu, wp->vaddr); > - g_array_remove_index(cpu->watchpoints, index); > + g_array_remove_index(wpts, index); > } > > /* Remove a specific watchpoint. */ > int cpu_watchpoint_remove(CPUState *cpu, vaddr addr, vaddr len, > int flags) > { > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); old... > CPUWatchpoint *wp; > - int i = 0; > + int retval = -ENOENT; > + > + if (unlikely(wpts) && unlikely(wpts->len)) { If this function is called, it's not so unlikely that cpu->watchpoints is NULL! > + int i = 0; > + > + qemu_mutex_lock(&cpu->update_debug_lock); > + wpts = rcu_copy_watchpoints(cpu); ... and new. > > - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { > do { > wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); > if (wp && addr == wp->vaddr && len == wp->len > && flags == (wp->flags & ~BP_WATCHPOINT_HIT)) { > - cpu_watchpoint_delete(cpu, i); > - return 0; > + cpu_watchpoint_delete(cpu, wpts, i); > + retval = 0; > + } else { > + i++; > } > - } while (i++ < cpu->watchpoints->len); > + } while (i < wpts->len); Please write the iteration in the same way from the beginning, to keep this patch as small as possible. > + rcu_update_watchpoints(cpu, wpts); Or free and set it to NULL if there are no watchpoints at all? > + qemu_mutex_unlock(&cpu->update_debug_lock); > + > } > > - return -ENOENT; > + return retval; > } > > /* Remove a specific watchpoint by external reference. */ > int cpu_watchpoint_remove_by_ref(CPUState *cpu, int ref) > { > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); > CPUWatchpoint *wp; > - int i = 0; > + int retval = -ENOENT; > + > + if (unlikely(wpts) && unlikely(wpts->len)) { > + int i = 0; > + > + qemu_mutex_lock(&cpu->update_debug_lock); > + wpts = rcu_copy_watchpoints(cpu); > > - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { > do { > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); > + wp = &g_array_index(wpts, CPUWatchpoint, i); > if (wp && wp->ref == ref) { > - cpu_watchpoint_delete(cpu, i); > - return 0; > + cpu_watchpoint_delete(cpu, wpts, i); > + retval = 0; > + } else { > + i++; > } > - } while (wp && i++ < cpu->watchpoints->len); > + } while (i < wpts->len); > + > + rcu_update_watchpoints(cpu, wpts); Same here, free and set it to NULL if the last watchpoint has been removed? A few of these suggestions probably apply to breakpoints as well. > + qemu_mutex_unlock(&cpu->update_debug_lock); > + > } > > - return -ENOENT; > + return retval; > } > > /* Remove all matching watchpoints. */ > void cpu_watchpoint_remove_all(CPUState *cpu, int mask) > { > + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); > CPUWatchpoint *wp; > > - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { > - int i = cpu->watchpoints->len; > + if (unlikely(wpts) && unlikely(wpts->len)) { > + int i = 0; > + > + qemu_mutex_lock(&cpu->update_debug_lock); > + wpts = rcu_copy_watchpoints(cpu); > + > do { > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); > + wp = &g_array_index(wpts, CPUWatchpoint, i); > if (wp->flags & mask) { > - cpu_watchpoint_delete(cpu, i); > + cpu_watchpoint_delete(cpu, wpts, i); > } else { > - i--; > + i++; > } > - } while (cpu->watchpoints->len && i >= 0); > + } while (i < wpts->len); > + > + rcu_update_watchpoints(cpu, wpts); > + qemu_mutex_unlock(&cpu->update_debug_lock); > } > } > > @@ -945,18 +1042,6 @@ static GArray *rcu_copy_breakpoints(CPUState *cpu) > return new; > } > > -struct BreakRCU { > - struct rcu_head rcu; > - GArray *bkpts; > -}; > - > -/* RCU reclaim step */ > -static void rcu_free_breakpoints(struct BreakRCU *rcu_free) > -{ > - g_array_free(rcu_free->bkpts, false); > - g_free(rcu_free); > -} > - > /* Called with update lock held */ > static void rcu_update_breakpoints(CPUState *cpu, GArray *new_bkpts) > { > @@ -964,9 +1049,9 @@ static void rcu_update_breakpoints(CPUState *cpu, GArray > *new_bkpts) > atomic_rcu_set(&cpu->breakpoints, new_bkpts); > > if (bpts) { > - struct BreakRCU *rcu_free = g_malloc(sizeof(*rcu_free)); > - rcu_free->bkpts = bpts; > - call_rcu(rcu_free, rcu_free_breakpoints, rcu); > + struct FreeDebugRCU *rcu_free = g_malloc(sizeof(*rcu_free)); > + rcu_free->debug = bpts; > + call_rcu(rcu_free, rcu_debug_free, rcu); > } > } > > @@ -2296,6 +2381,7 @@ static void check_watchpoint(int offset, int len, > MemTxAttrs attrs, int flags) > target_ulong pc, cs_base; > target_ulong vaddr; > uint32_t cpu_flags; > + GArray *wpts; > > if (cpu->watchpoint_hit) { > /* We re-entered the check after replacing the TB. Now raise > @@ -2306,11 +2392,12 @@ static void check_watchpoint(int offset, int len, > MemTxAttrs attrs, int flags) > } > vaddr = (cpu->mem_io_vaddr & TARGET_PAGE_MASK) + offset; > > - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { > + wpts = atomic_rcu_read(&cpu->watchpoints); > + if (unlikely(wpts) && unlikely(wpts->len)) { > CPUWatchpoint *wp; > int i; > - for (i = 0; i < cpu->watchpoints->len; i++) { > - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); > + for (i = 0; i < wpts->len; i++) { > + wp = &g_array_index(wpts, CPUWatchpoint, i); > if (cpu_watchpoint_address_matches(wp, vaddr, len) > && (wp->flags & flags)) { > if (flags == BP_MEM_READ) { >